Status of Forest Birds in Hawaiʻi Volcanoes National Park: Mixed Results for Native and Non-Native Species

Seth W. Judge, Kristina L. Paxton , Angela T. Beck, Richard J. Camp

Please cite this publication as:

Judge, S.W., K.L. Paxton, A.T. Beck, and R.J. Camp. 2026. Status of Forest Birds in Hawaiʻi Volcanoes National Park: Mixed Results for Native and Non-Native Species. Science Report NPS/SR—2026/440. National Park Service, Fort Collins, Colorado. https://doi.org/10.36967/2318341 

Abstract

Hawaiʻi Volcanoes National Park (HAVO) was surveyed for landbirds and landbird habitat in 2020 and 2021 as part of a long-term monitoring program. These surveys represent the third data point in a time series assessing landbird distribution, density, and abundance. Surveys were conducted across seven tracts totaling 15,375 ha using point-transect distance sampling to estimate population density and abundance. A total of 29 species were detected, including eight native and 21 non-native species. Changes in species-specific densities by tract were evaluated using two-sample z-tests within an equivalence testing framework to assess population change relative to surveys conducted in 2010. Results were mixed across tracts for most native species. ʻApapane (Himatione sanguinea) densities increased significantly in four tracts but decreased in the remaining three. Hawaiʻi ʻAmakihi (Chlorodrepanis v. virens) densities increased in the two largest tracts—Mauna Loa South Flank and Mauna Loa Strip—but decreased in the East Rift Zone and ʻŌlaʻa tracts, where the species has remained at low densities (<0.30 birds/ha) since 2010. Hawaiʻi ʻElepaio (Chasiempis sandwichensis) showed increases in the Honomalino, ʻŌlaʻa, and Pāpā tracts, but decreased by more than 60% in the Mauna Loa Strip and was absent from the Mauna Loa South Flank. The federally threatened ʻIʻiwi (Drepanis coccinea) was absent from the Mauna Loa Strip, where an estimated 2,417 ± 32 (SE) individuals were present in 2010, and was also undetected in three additional tracts where it had previously occurred. In contrast, ʻIʻiwi density increased significantly in the Honomalino tract, with an estimated 2021 abundance of 1,366 ± 26 birds. Differences of ’Ōma’o (Myadestes obscurus) were also mixed, with a notable increase in the Mauna Loa South Flank tract where we estimated an abundance of 3,035 ± 23 birds. Patterns also varied among non-native species. The Warbling White-eye (Zosterops japonicus) was the most abundant and broadly distributed non-native species, though densities declined significantly in five tracts. After being undetected in 2010, densities of the Japanese Bush Warbler (Horornis diphone) increased significantly in most tracts. The Northern Cardinal (Cardinalis cardinalis) and Red-billed Leiothrix (Leiothrix lutea) also increased across most surveyed areas. These findings highlight the continued vulnerability of native landbirds in HAVO to habitat degradation, invasive species, non-native predators, avian disease, and wildfire.

Bright red ʻiʻiwi perched sideways on a slender branch, its long curved bill touching a cluster of fresh green leaves, framed by dense dark‑green pūkiawe foliage in soft, shaded forest light.
ʻIʻiwi (Drepanis coccinea).

NPS / JANICE WEI

Acknowledgments

We would like to thank Ryan Monello, Kelly Kozar, Mark Wasser, and Kim Weisenborn of the Pacific Island Inventory and Monitoring Network. We also thank Shalan Crysdale, Mel Johanson, and Linda Schubert of The Nature Conservancy-Hawaiʻi for their cooperation. Thanks to Rhonda Loh, Travis Heinrich, and Keola Awong of the Resource Management Division of Hawaiʻi Volcanoes National Park for site permission and logistical support. Thanks to pilot David Okita of Volcano Helicopters for safe transport and logistical advice. Special thanks to Cari Lynn Squibb, Dean Sedgwick, Natalie Wronkiewicz, Lester Gebin, and Ashley Romero for their landbird survey expertise. We also thank Paul Radley and Christopher Warren for valuable suggestions that improved the report. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The views and conclusions in this article represent the views solely of the authors and of the U.S. Geological Survey. This product has been peer reviewed and approved for publication consistent with USGS Fundamental Science Practices (https://pubs.usgs.gov/circ/1367/).

Introduction

The Hawaiian Islands are home to approximately 30% of all species listed as threatened and endangered in the United States. This includes around 500 species of plants and animals, among them 27 species of seabirds, shorebirds, and landbirds (USFWS 2024). Losses to avifauna and their habitat began with the arrival of humans to the archipelago between 780 and 1130 CE (Athens et al. 2014; Kirch 2011). Lowland forests were cleared for agriculture and birds were hunted for food and feathers (Olson and James 1982, 1984). Predation by introduced species such as dogs (Canis familiaris) and Polynesian rats (Rattus exulans) contributed to population reductions (Banko and Banko 2009; Olson and James 1982). Following European contact in the late 18th century, new threats such as cats (Felis catus), black rats (Rattus rattus), Norway rats (Rattus norvegicus), and small Indian mongooses (Urva auropunctata) each caused declines through predation and competition for resources (Atkinson 1977; Banko 1992; Witmer and Shiels 2017). In 1826, the Southern house mosquito (Culex quinquefasciatus) was introduced, a species that is a competent vector for avian malaria (Plasmodium relictum; Warner 1968). Infected mosquitoes spread through native habitat and many Hawaiian birds, immunologically naïve to the disease, were heavily impacted (van Riper et al. 1986). The culmination of these threats resulted in an estimated 118 avian extinctions (Chesser et al. 2025; Olson and James 1982; VanderWerf et al. 2018).

This conservation crisis is ongoing, with eight landbird species recently delisted due to extinction (USFWS 2023). Hawaiian honeycreepers (Subfamily Carduelinae) have been particularly affected, with only 17 of the more than 50 historically documented species and subspecies remaining today. Of these, all but six honeycreepers are federally listed as threatened or endangered (Chesser et al. 2025; USFWS 2024; VanderWerf et al. 2018). On the Island of Hawaiʻi, nearly half of its endemic landbird species have gone extinct over the past millennium (Olson and James 1991; Walther and Hume 2016). Of the 11 surviving species, five are federally listed as threatened or endangered (USFWS 2024).

Despite decades of conservation investment, efforts have largely failed to halt the decline of honeycreepers, particularly those most vulnerable to avian malaria and habitat degradation. In contrast, other native species have responded more positively. For example, the Nēnē (Branta sandvicensis) was downlisted to threatened in 2019, and the ʻIo (Buteo solitarius) was delisted in 2020 (USFWS 2019, 2020). These successes highlight how large tracts of protected state and federal land can be used for mitigating threats and preserving biodiversity. Hawaiʻi Volcanoes National Park (HAVO) is a critical conservation area on the island, encompassing approximately 134,000 hectares (ha). Within its boundaries, small populations of three federally endangered landbirds persist: ʻAkiapōlāʻau (Hemignathus wilsoni), ʻAlawī (Hawaiʻi Creeper; Loxops mana), and Hawaiʻi ʻĀkepa (Loxops coccineus). The federally threatened ʻIʻiwi (Drepanis coccinea) inhabits HAVO, along with two additional Hawaiian honeycreepers, Hawaiʻi ʻAmakihi (Chlorodrepanis v. virens) and ʻApapane (Himatione sanguinea). The park also harbors populations of Hawaiʻi ʻElepaio (Chasiempis sandwichensis), a monarch flycatcher, and the ʻŌmaʻo (Myadestes obscurus), a Hawaiian thrush. Collectively, these species play vital ecological roles as pollinators, seed dispersers, and insectivores. They contribute to nutrient cycling and enrich soils for plants essential to the ecosystem. Hawaiian birds also hold significance in Hawaiian culture and tradition—species such as the ʻIʻiwi feature prominently in Hawaiian mythology, song, and dance. The conservation of native landbirds and their habitat not only preserves ecosystem function and biodiversity but also the cultural landscape of Hawaiʻi.

During the late 1970s and early 1980s, the U.S. Fish and Wildlife Service (USFWS) conducted surveys of bird and plant communities on the main Hawaiian Islands as part of the Hawaiian Forest Bird Survey (HFBS). Results from the survey indicated declining populations and decreasing ranges for most native species, and the extinction of several others (Scott and Kepler 1985; Scott et al. 1986). In 1976 and 1978, HFBS transects were surveyed in the Kaʻū and Kona regions of the Island of Hawaiʻi. The surveys revealed that areas of leeward and windward Mauna Loa harbored large populations of native birds and important native habitat. Surveys continued on most of the original HFBS transects in 1992, 1993, and 1994 (Gorresen et al. 2005). In 2003, HAVO acquired the 47,350 ha Kahuku Unit, increasing the total area of the park to over 134,750 ha. In 2005, landbird surveys were conducted within the Kahuku Unit and eastern areas of the park, both on HFBS transects and on newly established transects (Tweed et al. 2007). Like the original HFBS, results from those surveys again indicated that HAVO harbored habitat that is critically important to native bird populations, and many of the island’s other indigenous, endemic, and endangered flora and fauna.

Monitoring to track population changes of native Hawaiian birds has been critical for informing resource management actions and strategies (Camp et al. 2011). Most endangered species recovery plans propose population density target values that must be achieved before a population may be considered for delisting (USFWS 2006), and such estimates can only be achieved through frequent monitoring (Doremus and Pagel 2001; Tear et al. 1995). The National Park Service (NPS) created the Inventory and Monitoring Program (I&M) following the National Park Omnibus Management Act of 1998 to acquire data needed to support effective management and protection of native habitats located on park lands. The Pacific Island Inventory and Monitoring Network (PACN) is one of 32 I&M Networks that conduct natural resource inventories and long-term monitoring. The PACN landbird monitoring project tracks populations in HAVO, Haleakalā National Park, and the National Park of American Samoa. PACN first surveyed HAVO in 2010 on transects that Tweed et al. (2007) had surveyed and which were then prioritized and partitioned into eight distinct tracts by Camp et al. (2011) in the “Landbirds Vital Sign Monitoring Protocol – Pacific Island Network.” After the initial 2010 survey, the eight tracts were separated into two groups that could be surveyed over two consecutive years. In 2015, three tracts were surveyed in the eastern area of the park that was under NPS stewardship prior to 2003, colloquially referred to as “Old HAVO.” The remaining five tracts within the Kahuku Unit were surveyed in 2016. The 2015–2016 survey effort produced indices of occurrence and distribution of 28 species of landbirds (Judge et al. 2017). Density and abundance estimates were made for 11 species (five native and six non-native) and changes in densities were assessed for each.

In 2020–2021, the HAVO landbird monitoring survey was repeated, providing the third data point in a time series used to evaluate changes in landbird distribution, density, and abundance. The Old HAVO Unit was surveyed in 2020, and the Kahuku Unit was surveyed in 2021. Only four tracts were surveyed in the Kahuku Unit because the Kahuku Tract was surveyed in 2019 (Judge et al. 2024). These surveys allowed for estimation of abundance and assessment of population change for both native and non-native bird species within each of the seven tracts. This report documents the population status of five endemic passerines: Hawaiʻi ʻElepaio, ʻŌmaʻo, Hawaiʻi ʻAmakihi, ʻApapane, and the federally threatened ʻIʻiwi. Population estimates are also provided for seven non-native species: Eurasian Skylark (Alauda arvensis), House Finch (Haemorhous mexicanus), Japanese Bush Warbler (Horornis diphone), Northern Cardinal (Cardinalis cardinalis), Red-billed Leiothrix (Leiothrix lutea), Warbling White-eye (Zosterops japonicus), and Yellow-fronted Canary (Crithagra mozambica). Differences in density were assessed for each of these species. Density changes were evaluated relative to the 2010 survey where detections were sufficient; for species not detected in 2010, differences were assessed using data from the 2015 and/or 2016 surveys with two-sample z-tests. Indices of occurrence are reported for an additional 17 species detected during surveys. The federally endangered Hawaiian honeycreepers ʻAkiapōlāʻau, ʻAlawī, and Hawaiʻi ʻĀkepa were not detected within the survey area. These results are intended to inform and support management actions aimed at stabilizing and increasing native bird populations.

Methods

Survey Area

Bird and habitat data were collected from seven tracts located on Mauna Loa and Kīlauea volcanoes (Figure 1). The Old HAVO tracts were surveyed in 2020 and included the East Rift Zone, ʻŌlaʻa, and Mauna Loa Strip. The Kahuku Unit tracts were surveyed in 2021 and included Honomalino, Mauna Loa South Flank, Northwest Kahuku, and Pāpā. The majority of the tracts are within HAVO and managed by NPS, with the exception of Honomalino, of which approximately 65% is owned and managed by The Nature Conservancy, with the remaining 35% under HAVO stewardship.

Figure 1. Map titled “Landbird Monitoring Stations 2020–2021” depicting Hawaiʻi Volcanoes National Park on the Island of Hawaiʻi. The main map shows a gray shaded‑relief base with 100‑m elevation contours and major roads, overlaid by the park boundary in green. Within the park, yellow dashed outlines indicate discrete sampling areas labeled Northwest Kahuku and Papa–Honomalino along the southwest boundary, Mauna Loa South Flank in the central south, Mauna Loa Strip upslope to the north, ʻŌlaʻa on the eastern mid‑elevation forest, and East Rift Zone near the southeast coastline. Inside these sampling areas, black circles denote legacy landbird monitoring stations, and gray circles denote randomly located monitoring stations. A legend explaining symbols, a north arrow, a dual‑unit scale bar, and an inset map of Hawaiʻi Island showing the park’s position are included along the lower and right margins.
Figure 1. Hawaiʻi Volcanoes National Park landbird survey monitoring tracts (2020–2021).

NPS

Point-transect distance sampling was conducted according to a split panel design, with an approximately equal ratio of permanently established legacy stations to one-time-only random stations surveyed in each of the seven tracts within the 2020–2021 survey area (refer to Camp et al. 2011 for details). Stations were spaced at 200 m and 150 m intervals along legacy and random transects, respectively. The beginning, or first station, of the random transects was randomly chosen within some tracts that were easily accessible. In tracts that were remote and densely vegetated, the first station of the random transects were located 150 m from a randomly selected legacy transect station and the direction of the transect was a randomly selected azimuth in degrees. A total of 450 stations were sampled during the 2020–2021 survey effort.

The elevation of all tracts ranged between 731 m and 2,560 m, which falls within three elevation zones: lowland, montane, and subalpine. Each elevation zone can be further described by three moisture regimes: dry, mesic, and/or wet (Green et al. 2015; Price et al. 2007). The frequent volcanic eruptions of Kīlauea and Mauna Loa have created a diversity of substrate ages ranging from <200 to approximately 10,000 years old (Wolfe and Morris 1996). “Kīpuka” features are common in most tracts; the Hawaiian term describes areas of remnant older-growth forest surrounded completely by younger lava flows to form an “island” of forest. Kīpuka and lava flows form forests of various stages of succession that contribute to habitat complexity and biodiversity in HAVO. The native ʻōhiʻa lehua (hereafter ʻōhiʻa; Metrosideros polymorpha) and koa (Acacia koa) trees are nearly ubiquitous throughout the survey area. Native shrubs such as pūkiawe (Leptecophylla tameiameiae), ʻōhelo ʻai (Vaccinium reticulatum), and ʻaʻaliʻi (Dodonaea viscosa) occur commonly in various combinations, with other native shrubs, small trees, and ferns. We used vegetation classifications and maps of HAVO produced by Green et al. (2015) to characterize the vegetation in each tract. Classifications are described by levels of predominant vegetation strata. Each level is separated by “/” in order of dominance, while co-dominant strata are indicated by a “-”, and strata in parentheses () indicate a species that may or may not be present. Vegetation strata are then followed by elevation zone and physiognomy of the vegetation (i.e., herbaceous, forest and woodlands, shrublands, and sparse vegetation). Each Green et al. (2015) vegetation classification follows the U.S. National Vegetation Classification Standard (Grossman et al. 1998) and is capitalized for clarity and consistency (e.g., ʻŌhi’a / Uluhe [Dicranopteris linearis] Lowland Mesic Woodland).

Tract Descriptions

East Rift Zone

The 2,254 ha East Rift Zone tract is located on the southeastern flank of Kīlauea volcano (Figure 2). The area had been volcanically active since 1983, with numerous eruptive events occurring until 2018, when a Kīlauea eruption along the Lower East Rift Zone led to the subsequent pause in activity in the tract and surrounding area. The tract is managed by HAVO and offers recreational activities such as hiking and camping, as well as geological research. The tract is a mosaic of bare recent lava flows to dense forest, with extensive craters and deep earth fissures throughout. The predominant vegetation classification is ʻŌhi’a / Hāpuʻu spp. (Cibotium spp.) Montane Wet Forest, with smaller areas of ʻŌhi’a / Uluhe Lowland Mesic Woodland (Green et al. 2015). Four legacy transects (totaling 55 stations) with stations spaced at 150 m and 200 m intervals were surveyed in 2020 (Figure 2). Randomly prescribed transects were abandoned after 2010 because of safety concerns. The tract is partially fenced and feral pigs (Sus scrofa) roam through much of the area.

Figure 2. This figure displays a satellite view of mixed wet forest and recent lava flows, with the NPS boundary in bright green and an irregular dashed white polygon marking the sampling frame. Blue legacy stations trace a curved path that follows the main road and rift features, forming a hooked loop through the central forested area; some unsampled legacy stations appear as black dots. The scale bar indicates transects are about 0–1 km long, illustrating how surveys track the accessible portions of the East Rift Zone.
Figure 2. The East Rift Zone landbird monitoring tract surveyed in 2020.

NPS

Honomalino

The 1,688 ha Honomalino tract is located on the leeward (southwestern) side of Mauna Loa and includes 597 ha within HAVO (Figure 3). The remaining 1,091 ha area of forested land is managed by The Nature Conservancy (TNC) in their 3,273 ha Kona Hema Preserve. The HAVO portion of the tract is predominantly ʻŌhi’a / Pūkiawe – ʻAʻaliʻi Montane Woodland, with smaller areas of ʻŌhi’a / Meadow Ricegrass (Microlaena stipoides) Semi-natural Woodland, plus areas of unvegetated lava. The TNC portion of the tract is a mix of bare lava and mesic koa and ʻōhi’a montane forest. TNC’s successful management has kept the preserve mostly ungulate-free. Two legacy transects totaling 46 stations and three random transects totaling 33 stations were surveyed in 2021.

Figure 3. The figure shows a rectangular sampling frame outlined in dashed white within the green NPS and adjacent Kona Hema Preserve (managed by The Nature Conservancy) boundaries over mixed forest and lava flows. Long rows of blue legacy stations cross the tract from west to east near the top and bottom edges, while yellow random stations form two diagonal transects that cut across the center of the frame. Background imagery highlights lava fingers and forest patches, with a north arrow and scale bar showing that stations span about 0–1.5 km across the Honomalino unit.
Figure 3. The Honomalino landbird monitoring tract surveyed in 2021. Areas within the Landbird Sampling Frame but to the left (west) of the park boundary are outside of Hawaiʻi Volcanoes National Park and are managed by The Nature Conservancy as the Kona Hema Preserve.

NPS

Mauna Loa South Flank

The 4,593 ha Mauna Loa South Flank tract lies in the southern portion of the Kahuku Unit on Mauna Loa (Figure 4). Extensive vegetation clearing for cattle (Bos taurus) ranching, along with impacts from European mouflon sheep (O. aries musimon), has substantially altered canopy cover and understory composition from the tract’s original condition as mesic and wet koa – ʻōhiʻa forest (Tweed et al. 2007). The vegetation is predominantly classified as ʻŌhi’a / Kikuyu Grass (Cenchrus clandestinus) Semi-natural Woodland, which consists of former pasture lands dominated by Kikuyu grass, meadow ricegrass, and marsh bristlegrass (Setaria parviflora), with small stands of ʻōhi’a-dominated native forest with native shrubs such as māmaki (Pipturus albidus), ʻākala (Rubus hawaiensis), and pūkiawe common throughout. Above 1,100 m elevation, areas of Koa / ʻŌhi’a Montane Dry Woodland predominate landbird monitoring stations. One legacy transect totaling 47 stations was surveyed in 2021. The randomly prescribed transects were not completed because of logistical constraints.

Figure 4. The map shows a tall, narrow sampling frame outlined in dashed white within the broader green NPS boundary over pasture and forest mosaics. A continuous column of blue legacy stations runs almost the full height of the frame, aligned along an old ranch road or contour. The north arrow and scale bar indicate the transect extends roughly 0–3 km, emphasizing the linear nature of sampling on the Mauna Loa South Flank.
Figure 4. The Mauna Loa South Flank landbird monitoring tract surveyed in 2021.

NPS

Mauna Loa Strip

The 3,181 ha Mauna Loa Strip tract is located on the eastern flank of Mauna Loa (Figure 5). The tract is situated along the paved 18 km Mauna Loa summit trail access road (a.k.a. “Strip Road”). The tract is a mosaic of Koa / Non-native Grass Semi-natural Woodland, Pūkiawe – ’A’ali’i Montane Shrubland, Koa / Pūkiawe Montane Woodland, Pūkiawe – ’A’ali’i Montane Sparse Vegetation, and unvegetated lava flows. HAVO Resource Management has kept the tract free of ungulates. Kapāpala Ranch and Kapāpala Forest Reserve lie adjacent to the tract’s southern boundary. The Kamehameha Land Assets Division, in partnership with the Three Mountain Alliance, manages the Keauhou Ranch to the north, an area that has been converted from an active cattle ranch to an area primarily managed for conservation. Three legacy transects totaling 40 stations and five random transects totaling 51 stations were surveyed in 2020 (Figure 5).

Figure 5. The figure depicts an oblong sampling frame paralleling the Mauna Loa summit road, outlined in dashed white inside the green park boundary over a patchwork of forest, shrubland, and lava. Blue legacy stations form several straight transects roughly perpendicular to the road, while yellow random stations interleave between them, creating a ladder-like pattern across the strip. A north arrow and dual-scale bar show that the combined transects span about 0–2 km across the Mauna Loa Strip, capturing the elevation and habitat gradient along the road corridor.
Figure 5. The Mauna Loa Strip landbird monitoring tract surveyed in 2020.

NPS

Northwest Kahuku

The 884 ha Northwest Kahuku tract is in the northwest corner of HAVO, on the leeward side of Mauna Loa (Figure 6). The tract comprises a patchwork of vegetation classifications, such as: Māmane / Meadow Ricegrass Subalpine Semi-natural Woodland, Māmane – (Pūkiawe – ’A’ali’i) Montane Woodland, Māmane (Sophora chrysophylla), Montane Sparse Vegetation, Naio (Myoporum sandwicense) Subalpine Woodland, Kikuyu Grass Semi-natural Herbaceous Vegetation, unvegetated lava, and others. The tract spans two climate zones: moderately dry and very dry (Price et al. 2007). There were well-established populations of feral sheep (Ovis aries) and some European mouflon sheep in the tract, resulting in little native understory throughout. Five legacy transects totaling 47 stations and five random transects totaling 25 stations were surveyed in 2021.

Figure 6. The figure is a satellite basemap of the Northwest Kahuku tract with the NPS boundary in bright green and the landbird sampling frame in a dashed white polygon. Blue points mark evenly spaced legacy point-count stations, while yellow points show the layout of newer random stations clustered toward the tract interior. A north arrow and dual‐scale bar (kilometers and miles) appear at the bottom, emphasizing that the transects span roughly 0–2 km across the unit.
Figure 6. The Northwest Kahuku landbird monitoring tract surveyed in 2021.

NPS

ʻŌlaʻa

The 2,446 ha ʻŌlaʻa tract is located on the eastern flank of Mauna Loa (Figure 7). The moderately wet (Price et al. 2007) forest grows on deep ash soils and is dominated by ʻōhi’a trees, with ʻōlapa (Cheirodendron trigynum), hāpuʻu (Cibotium spp.) and ʻākala prevalent, with some areas dominated by non-native kāhili ginger (Hedychium gardnerianum). Koa was present in the northern areas of the tract. The vegetation is predominantly classified as ʻŌhi’a – ʻŌlapa / (Hāpuʻu spp.) Montane Wet Forest. The tract has been divided into smaller sections: New Unit, Ag Unit, Koa Unit, Puʻu Unit, and Small Tract. Most of the units are fenced and free of ungulates. Five legacy transects totaling 47 stations and five random transects totaling 48 stations, between 1,067 m and 1,341 m elevation, were surveyed in 2020.

Figure 7. The image is an aerial view of dense green forest of the ʻŌlaʻa tract within Hawaiʻi Volcanoes National Park. The tract inferenca area boundary is outlined bright green. Dashed lines represent fences that divide the tract into seven smaller units. Legacy point-count stations form four straight blue transects in the same cardinal direction, while yellow random stations branch off these lines into segments roughly ten stations long. A north arrow and scale bar at the bottom indicate transects extend about 0–2 km across the interior.
Figure 7. The ʻŌlaʻa landbird monitoring tract surveyed in 2020, with different NPS Management Units labeled.

NPS

Pāpā

The 329 ha Pāpā tract is located 2.5 km north of the Honomalino tract on leeward Mauna Loa (Figure 8). The tract lies completely within HAVO but is accessed through TNC’s Kona Hema Preserve. The tract is predominantly ʻŌhi’a / Pūkiawe – ’A’ali’i Montane Woodland, with an understory that also includes the native grasses Deschampsia nubigena and Morelotia gahniiformis, plus areas of unvegetated lava. Two legacy transects totaling 11 stations were surveyed in 2021. Surveyors were unable to complete stations on the randomly prescribed transects.

Figure 8. The image presents a small, tilted polygon (the landbird sampling frame) drawn in dashed white inside the green NPS boundary over aerial imagery of patchy forest and lava. A single row of blue legacy stations runs diagonally across the upper portion of the frame, with a few additional stations scattered downslope near the forest–lava boundary. The north arrow and short scale bar show that the entire transect network is less than 1 km long and occupies only a small subsection of the Pāpā tract.
Figure 8. The Pāpā landbird monitoring tract surveyed in 2021.

NPS

Landbird Sampling

Surveys in the Old HAVO tracts (East Rift Zone, Mauna Loa Strip Road, and ʻŌlaʻa) were conducted from 16 March 2020 through 24 June 2020. Surveys in the Kahuku tracts (Honomalino, Mauna Loa South Flank, Northwest Kahuku, and Pāpā) were conducted from 6 April 2021 through 16 June 2021. In the weeks prior to the start of the survey, primary and secondary surveyors were trained to calibrate distance estimation and learn bird vocalizations, thereby minimizing variability among observers and standardizing for local conditions (Camp et al. 2011). Detection type (heard, seen, or both) and horizontal distance from the station center point to individual birds detected was recorded during the 8-minute count. Birds only flying over or through the survey area were excluded. Detections of both male and female birds singing and calling were recorded, although the sex of individuals was not noted. Most of the birds encountered were adults because counts occurred during the breeding season and most juveniles had not yet fledged (Camp et al. 2011).

Observers also recorded cloud cover, rain, wind, gust, and time of day at each station (Camp et al. 2011). Sampling was conducted between dawn and 11:00 a.m. and halted when rain, wind strength, or gust exceeded prescribed levels (light rain and wind level 3 on the Beaufort scale). Weather variables and time of day were included as covariates in the analyses to account for possible differences in the detection probabilities due to the conditions when the count was conducted.

The detectability of forest birds varies throughout the year due to changes in vocal activity associated with breeding (Best 1981), and birds may move in or out of the study area in response to phenology of food resources (Simon et al. 2002). To minimize biases associated with differences in sampling periods, sampling was restricted to the breeding season only.

Data Analysis

Indices

Indices of bird occurrence were calculated for each species. Percent occurrence was calculated as the number of stations occupied divided by the total number of stations sampled. Similarly, birds per count (BPC) was calculated as the total number of individuals detected divided by the total number of station counts. Detections of each species were mapped with vegetation strata published by Green et al. (2015). Detections were also described by habitat data collected at each station in 2020–2021.

Density Estimation

Species-specific density estimates were calculated for twelve species with sufficient detections to adequately characterize detection probability (Buckland et al. 2015) using the R (R Core Team 2024 package DISTANCE (Miller et al. 2019), following methods described in Thomas et al. (2010). Candidate detection function models were limited to half-normal and hazard-rate forms with expansion series of order two. Half-normal models were paired with cosine and Hermite polynomial adjustments, and hazard-rate models were paired with cosine and simple polynomial adjustments. Model precision was improved by incorporating sampling covariates within the multiple-covariate distance sampling (MCDS) engine of DISTANCE (Buckland et al. 2015). Covariates included cloud cover, rain intensity, wind strength, gust strength, observer, detection type, and survey year (NPS Datastore - Distance-sampling model selection and Akaike's Information Criterion (AIC) Statistics).

For each species, detectability models in the candidate set were fit to data pooled across survey years, and the model with the lowest Akaike’s Information Criterion (AIC) value was selected (Buckland et al. 2015). Data were truncated at a distance corresponding to an estimated detection probability of approximately 0.1 under a preliminary half-normal detection function. This truncation reduces the influence of outliers and decreases the number of parameters required to model the detection function. Species-specific density estimates by tract and survey year were derived from the global detection function using post-stratification procedures, and variances and confidence intervals were estimated using bootstrap methods with 1,000 iterations in DISTANCE (NPS Datastore - Distance-sampling model selection and Akaike's Information Criterion (AIC) Statistics; Thomas et al. 2010). Absolute abundance was calculated as the mean of tract-level density estimates weighted by tract area for each species.

Differences between 2010 and 2020–2021 population densities were evaluated using a two-sample z-test within an equivalency framework following Camp et al. (2008). Population change was assessed over a 10-year period (2010–2020) for most species; however, species occurring in the Kahuku Unit were evaluated over an 11-year period because those tracts were surveyed in 2010 and 2021. For species not detected in 2010, changes in density were assessed between surveys conducted over a 5-year period (2015–2016 and 2020–2021). For example, the Japanese Bush Warbler was not detected in any of the seven tracts surveyed in 2010 (Judge et al. 2011). Population change was classified as a significant increase, significant decrease, or negligible (a statistically significant but biologically small increase or decrease in density).

Habitat Sampling

Habitat data were collected following the methods described in Camp et al. (2011). A 50 m radius plot was established at each survey station using the station as the center. At each plot, the dominant canopy species composition, canopy height and cover, and dominant understory species composition were recorded (Jacobi 1989). Habitat surveys were collected at the point-count stations after completing bird counts (either after completing the station count or after completing the daily counts).

Computer Data Entry and Verification Methods

Microsoft Access was used as the primary software environment for landbirds data and the associated metadata. An Access database with front-end, back-end configuration was developed for the landbird monitoring and habitat data and is available online (DataStore - Pacific Island Network Landbird Monitoring).

Raw data were verified by comparing data sheets to the electronic version on a line-by-line basis to correct transcription errors. After line-by-line proofing was completed, individual data sets were certified by checking for errors. Lastly, field books (copies and originals) and digital data were archived according to PACN standards.

Results

2020–2021 Landbird Results

Composition, Distribution, and Occurrence

A total of 14,061 birds of 29 species (eight native and 21 non-native) were detected during the 2020–2021 landbird survey (Tables 1 and 2). ʻApapane and Hawaiʻi ʻAmakihi were the most widely distributed native birds detected, occurring at 87.1% and 63.8% of the 450 stations surveyed, respectively. Occurrence of ʻApapane ranged between 87.3% to 100% for every tract except Northwest Kahuku, where it occurred at 47.1% of stations (Table 3). Occurrence of Hawaiʻi ʻAmakihi exceeded 90% in the Mauna Loa Strip, Mauna Loa South Flank, Honomalino, and Pāpā tracts, but the species occurred at <2% of stations within the East Rift Zone tract and it was absent altogether from the ʻŌlaʻa tract. ’Ōmaʻo and Hawaiʻi ʻElepaio occurred at 25.8% and 19.1% of total stations surveyed, respectively. Occurrence of ’Ōma’o ranged from 24.2% to 70.9% of stations surveyed in the windward East Rift Zone, Mauna Loa Strip, Mauna Loa South Flank, and ʻŌlaʻa tracts, but the species was absent from the leeward Honomalino, Pāpā, and Northwest Kahuku tracts. The Hawaiʻi ʻElepaio was absent only from the East Rift Zone tract; a single individual was detected in Northwest Kahuku, and occurrence in the remaining tracts ranged up to 53.2% in Honomalino. There were 19 detections of the federally threatened ʻIʻiwi, which only occurred within the Honomalino tract at 13.9% of stations surveyed. There were 10 total detections of ʻIo; the detections occurred only in the Mauna Loa South Flank and ʻŌlaʻa tracts. There was a single detection of Pueo (Asio flammeus sandwichensis) in the Northwest Kahuku tract, and there were seven detections of Nēnē, all within the Mauna Loa South Flank tract. None of the three federally endangered species—Hawaiʻi ʻĀkepa, ʻAlawī, and ʻAkiapōlāʻau—were detected.

Table 1. List of species detected during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. Taxonomic classification follows the International Ornithological Congress (IOC) World Bird List (Gill et al. 2026), except for Nēnē (Hawaiian Goose) and ʻIo (Hawaiian Hawk), for which their Hawaiian name hasn’t been recognized. The origin (E = endemic and NN = non-native) of each species is presented.
Common Name Scientific Name Origin
African Silverbill Euodice cantans NN
American Barn Owl Tyto furcata NN
ʻApapane Himatione sanguinea E
California Quail Callipepla californica NN
Chinese Hwamei Garrulax canorus NN
Common Myna Acridotheres tristis NN
Common Waxbill Estrilda astrild NN
Erckel’s Spurfowl Pternistis erckelii NN
Eurasian Skylark Alauda arvensis NN
Hawaiʻi ʻAmakihi Chlorodrepanis virens virens E
Hawaiʻi ʻElepaio Chasiempis sandwichensis E
House Finch Haemorhous mexicanus NN
’I’iwi Drepanis coccinea E
ʻIo (Hawaiian Hawk) Buteo solitarius E
Japanese Bush Warbler Horornis diphone NN
Kalij Pheasant Lophura leucomelanos NN
Nēnē (Hawaiian Goose) Branta sandvicensis E
Northern Cardinal Cardinalis cardinalis NN
Northern Mockingbird Mimus polyglottos NN
’Ōma’o Myadestes obscurus E
Pueo Asio flammeus sandwichensis E
Red-billed Leiothrix Leiothrix lutea NN
Scaly-breasted Munia Lonchura punctulata NN
Spotted Dove Spilopelia chinensis NN
Warbling White-eye Zosterops japonicus NN
Wild Turkey Meleagris gallopavo NN
Yellow-billed Cardinal Paroaria capitata NN
Yellow-fronted Canary Crithagra mozambica NN
Zebra Dove Geopelia striata NN

Table 2. Total native and non-native bird detections recorded during the 2020–2021 Hawaiʻi Volcanoes National Park landbird monitoring survey. Total detections (n) represent the number of birds recorded during 458 counts at 450 stations across seven distinct monitoring tracts. Stations occupied indicates the number of stations with one or more detections of a species. Percent occurrence was calculated as the proportion of stations occupied relative to the total number of stations surveyed. Birds per count (BPC) was calculated as total detections divided by the number of counts.
Common Name n Stations Occupied Occurrence BPC
African Silverbill 6 4 0.2% 0.01
American Barn Owl 1 1 0.9% <0.01
ʻApapane 1,876 392 87.1% 4.14
California Quail 38 23 5.1% 0.07
Chinese Hwamei 24 21 4.7% 0.05
Common Myna 2 2 0.4% <0.01
Common Waxbill 20 8 1.8% 0.04
Erckel’s Spurfowl 259 143 31.8% 0.55
Eurasian Skylark 21 17 3.8% 0.04
Hawaiʻi ʻAmakihi 1,411 287 63.8% 3.11
Hawaiʻi ʻElepaio 171 86 19.1% 0.38
House Finch 225 107 23.8% 0.48
ʻIʻiwi 19 11 2.4% 0.04
ʻIo 10 9 2.0% 0.02
Japanese Bush Warbler 254 128 28.4% 0.56
Kalij Pheasant 16 12 2.7% 0.03
Nēnē 7 2 0.4% 0.02
Northern Cardinal 304 198 44.0% 0.67
Northern Mockingbird 44 34 7.6% 0.09
’Ōma’o 187 116 25.8% 0.41
Pueo 1 1 0.2% <0.01
Red-billed Leiothrix 196 121 26.9% 0.42
Scaly-breasted Munia 4 3 0.7% 0.01
Spotted Dove 5 5 1.1% 0.01
Warbling White-eye 1,356 329 73.1% 2.95
Wild Turkey 5 3 0.7% 0.01
Yellow-billed Cardinal 1 1 0.2% <0.01
Yellow-fronted Canary 83 51 11.3% 0.18
Zebra Dove 3 3 0.7% 0.01

Table 3. Indices of native and non-native bird detections recorded within each tract during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. Total detections (n) represent the number of individual birds recorded during all counts conducted within each tract (the number of stations and counts per tract are shown in parentheses beneath each tract name). Stations occupied indicates the number of stations at which one or more individuals of a species were detected. Percent occurrence was calculated as stations occupied divided by the total number of stations surveyed. Birds per count (BPC) was calculated as total detections divided by the total number of counts.
Tract Common Name n Stations Occupied Occurrence BPC
East Rift Zone
(Stations = 55,
Counts = 56)		 American Barn Owl 1 1 1.1% 0.01
ʻApapane 205 48 87.3% 3.66
Chinese Hwamei 7 7 12.7% 0.13
Hawaiʻi ʻAmakihi 3 1 1.8% 0.05
Japanese Bush Warbler 99 39 70.9% 1.77
Northern Cardinal 21 13 23.6% 0.38
’Ōma’o 70 39 70.9% 1.25
Warbling White-eye 337 54 98.2% 6.02
Yellow-billed Cardinal 1 1 1.8% 0.02
Yellow-fronted Canary 11 8 14.5% 0.20
Mauna Loa Strip (Stations = 91,
Counts = 91)		 ʻApapane 467 89 97.8% 5.13
California Quail 6 4 4.4% 0.07
Chinese Hwamei 17 14 15.4% 0.19
Common Waxbill 9 4 4.4% 0.10
Common Myna 1 1 1.1% 0.01
Erckel’s Spurfowl 77 51 56.0% 0.85
Eurasian Skylark 1 1 1.1% 0.01
Hawaiʻi ʻAmakihi 325 82 90.1% 3.57
Hawaiʻi ʻElepaio 40 26 28.6% 0.44
House Finch 21 14 15.4% 0.23
Japanese Bush Warbler 38 23 25.3% 0.42
Kalij Pheasant 5 2 2.2% 0.05
Northern Cardinal 84 48 52.7% 0.92
’Ōma’o 45 33 36.3% 0.49
Red-billed Leiothrix 67 42 46.2% 0.74
Scaly-breasted Munia 2 1 1.1% 0.02
Spotted Dove 2 2 2.2% 0.02
Warbling White-eye 321 83 91.2% 3.53
Yellow-fronted Canary 34 19 20.9% 0.37
ʻŌlaʻa
(Stations = 95,
Counts = 97)		 ʻApapane 293 89 93.7% 3.02
Common Myna 1 1 1.1% 0.01
Hawaiʻi ʻElepaio 19 14 14.7% 0.20
ʻIo 5 5 5.3% 0.05
Japanese Bush Warbler 74 44 46.3% 0.76
Northern Cardinal 25 23 24.2% 0.26
’Ōma’o 42 23 24.2% 0.43
Red-billed Leiothrix 81 47 49.5% 0.84
Spotted Dove 3 3 3.2% 0.03
Warbling White-eye 472 95 100% 4.87
Honomalino
(Stations = 79,
Counts = 79)		 ʻApapane 576 79 100% 7.29
Erckel’s Spurfowl 53 37 46.8% 0.67
Hawaiʻi ʻAmakihi 422 76 96.2% 5.34
Hawaiʻi ʻElepaio 108 42 53.2% 1.37
House Finch 25 14 17.7% 0.32
ʻIʻiwi 19 11 13.9% 0.24
Japanese Bush Warbler 41 20 25.3% 0.52
Kalij Pheasant 5 4 5.1% 0.06
Northern Cardinal 93 57 72.2% 1.18
Red-billed Leiothrix 35 25 31.6% 0.44
Warbling White-eye 81 45 57.0% 1.03
Yellow-fronted Canary 4 4 5.1% 0.05
Zebra Dove 3 3 3.8% 0.04
Mauna Loa South Flank
(Stations = 47,
Counts = 47)		 African Silverbill 6 4 8.5% 0.13
ʻApapane 203 42 89.4% 4.32
Common Waxbill 11 4 8.5% 0.23
Erckel’s Spurfowl 3 2 4.3% 0.06
Hawaiʻi ʻAmakihi 230 47 100% 4.89
Hawaiʻi ʻElepaio 1 1 2.1% 0.02
House Finch 31 17 36.2% 0.66
ʻIo 5 4 8.5% 0.11
Kalij Pheasant 4 4 8.5% 0.09
Nēnē 7 2 4.3% 0.15
Northern Cardinal 48 32 68.1% 1.02
’Ōma’o 30 21 44.7% 0.64
Red-billed Leiothrix 10 6 12.8% 0.21
Scaly-breasted Munia 2 2 4.3% 0.04
Warbling White-eye 137 47 100% 2.91
Yellow-fronted Canary 34 20 42.6% 0.72
Northwest Kahuku
(Stations = 72,
Counts = 75)		 ʻApapane 65 34 47.2% 0.87
California Quail 32 19 26.4% 0.43
Erckel’s Spurfowl 121 50 69.4% 1.61
Eurasian Skylark 20 16 22.2% 0.27
Hawaiʻi ʻAmakihi 400 72 100% 5.33
Hawaiʻi ʻElepaio 1 1 1.4% 0.01
House Finch 148 62 86.1% 1.97
Kalij Pheasant 2 2 2.8% 0.03
Northern Cardinal 24 18 25.0% 0.32
Northern Mockingbird 44 34 47.2% 0.59
Pueo 1 1 1.4% 0.01
Warbling White-eye 8 5 6.9% 0.11
Wild Turkey 5 3 4.2% 0.07
Pāpā
(Stations = 11,
Counts = 11)		 ʻApapane 67 11 100% 6.09
Erckel’s Spurfowl 5 3 27.3% 0.45
Hawaiʻi ʻAmakihi 31 9 81.8% 2.82
Hawaiʻi ʻElepaio 2 2 18.2% 0.18
Japanese Bush Warbler 2 2 18.2% 0.18
Northern Cardinal 9 7 63.6% 0.82
Red-billed Leiothrix 3 1 9.1% 0.27

The Warbling White-eye was the most broadly distributed non-native species, occurring at 73.1% of total stations surveyed. Occurrence exceeded 90% in every tract except Northwest Kahuku, where it was detected at 6.9% of stations sampled, and in the Pāpā tract, where it was absent. The Northern Cardinal, Erckel’s Spurfowl (Pternistis erckelii), Japanese Bush Warbler, House Finch, Red-billed Leiothrix, and Yellow-fronted Canary had the next highest occurrences of non-native species. The remaining 10 species occurred at less than 10% of stations surveyed. Each non-native species had a patchy distribution that will be described further in “Species Summaries” below. Maps of occurrence for every species detected are provided in the Appendix and referenced in each species summary.

Population Density, Abundance, and Change

There were sufficient detections of 12 species (five native and seven non-native) to allow for density and abundance estimation within all or most of the tracts surveyed and for every survey year: 2010, 2015–2016, and 2020–2021. The estimates are provided in individual tables for each of the 12 species in the “Species Summaries” section below.

Differences in population density and abundance varied by species and tract, with both significant increases and decreases observed between 2010 and 2020–2021. Most species exhibited incremental declines across survey periods; however, some showed non-linear temporal patterns, with densities peaking in 2015–2016 and subsequently decreasing by 2020–2021, or, in other cases, decreasing initially and increasing in the most recent survey. As a result, net changes between the earliest and most recent surveys sometimes contrasted with changes observed between 2015–2016 and 2020–2021, such that increases or decreases reflect endpoint differences rather than consistent directional change through time. These contrasting patterns were uncommon and are addressed in greater detail in the species summaries.

The largest increase among native species was for Hawaiʻi ʻElepaio in the Honomalino tract, which rose significantly by +8.37 ± 0.11 (difference ± SE) birds/ha (Table 4). ʻApapane and ʻIʻiwi also increased significantly in Honomalino, by +2.73 ± 0.07 and +0.17 ± 0.02 birds/ha, respectively. In the Mauna Loa South Flank tract, densities of ʻApapane, Hawaiʻi ʻAmakihi, and ’Ōma’o increased, while in the ʻŌlaʻa tract, notable increases were observed for Hawaiʻi ʻElepaio and ’Ōma’o.

Table 4. Differences in bird densities during the 2020–2021 surveys compared to 2010 within each tract of the Hawai’i Volcanoes National Park survey area. The null hypothesis of no change in density over time was tested using a z-test. Equivalence tests determined whether observed changes fell within threshold bounds (0.0093; −0.0199) corresponding to a 25% change in density over 25 years. LCI and UCI refer to lower and upper 90% confidence intervals; LEL and UEL represent lower and upper equivalence levels (t-values); LELp and UELp are the associated p-values.
Tract Species Names Difference SE LCI UCI z-test p LEL UEL LELp UELp Change B
East Rift Zone ʻApapane −11.81 0.14 −12.04 −11.59 <0.01 84.40 −86.08 1.00 <0.01 Significant decrease
Hawaiʻi ʻAmakihi −0.09 0.01 −0.10 −0.08 <0.01 −7.32 −30.58 <0.01 <0.01 Negligible decrease
Japanese Bush Warbler A 0.22 0.01 0.21 0.24 <0.01 −37.89 23.69 <0.01 1.00 Significant increase
Northern Cardinal 0.25 0.01 0.24 0.26 <0.01 −71.83 27.98 <0.01 1.00 Significant increase
ʻŌʻmao −0.70 0.02 −0.73 −0.67 <0.01 32.05 −45.18 1.00 <0.01 Significant decrease
Red-billed Leiothrix −0.12 <0.01 −0.13 −0.12 <0.01 −1.66 −52.72 0.05 <0.01 Negligible decrease
Warbling White-eye 7.35 0.16 7.09 7.62 <0.01 −46.31 44.86 <0.01 1.00 Significant increase
Yellow-fronted Canary A 0.31 0.01 0.31 0.32 <0.01 −74.67 53.49 <0.01 1.00 Significant increase
Honomalino ʻApapane 2.73 0.07 2.61 2.86 <0.01 −38.28 35.17 <0.01 1.00 Significant increase
Hawaiʻi ʻAmakihi −1.35 0.12 −1.54 −1.16 <0.01 10.54 −12.56 1.00 <0.01 Significant decrease
Hawaiʻi ʻElepaio 8.37 0.11 8.20 8.55 <0.01 −79.38 77.20 <0.01 1.00 Significant increase
House Finch −1.64 0.02 −1.68 −1.61 <0.01 76.40 −88.17 1.00 <0.01 Significant decrease
ʻIʻiwi 0.17 0.02 0.14 0.20 <0.01 −16.86 3.92 <0.01 1.00 Significant increase
Japanese Bush Warbler A 0.26 <0.01 0.26 0.26 <0.01 −116.03 77.58 <0.01 1.00 Significant increase
Northern Cardinal 0.31 0.01 0.30 0.32 <0.01 −79.64 37.52 <0.01 1.00 Significant increase
Red-billed Leiothrix 0.72 0.01 0.71 0.73 <0.01 −131.33 95.50 <0.01 1.00 Significant increase
Warbling White-eye −1.92 0.04 −1.99 −1.86 <0.01 46.49 −52.54 1.00 <0.01 Significant decrease
Yellow-fronted Canary A −0.53 0.01 −0.54 −0.52 <0.01 68.97 −84.50 1.00 <0.01 Significant decrease
Mauna Loa South Flank ʻApapane 3.11 0.06 3.01 3.21 <0.01 −53.98 50.09 <0.01 1.00 Significant increase
Eurasian Skylark A −0.01 <0.01 −0.01 −0.01 <0.01 −227.30 −276.60 <0.01 <0.01 Negligible decrease
Hawaiʻi ʻAmakihi 0.50 0.06 0.40 0.60 <0.01 −10.69 6.75 <0.01 1.00 Significant increase
House Finch −2.37 0.02 −2.40 −2.34 <0.01 118.21 −130.51 1.00 <0.01 Significant decrease
Japanese Bush Warbler A −0.04 <0.01 −0.04 −0.04 <0.01 −23.51 −132.59 <0.01 <0.01 Negligible decrease
Northern Cardinal 0.20 0.01 0.19 0.21 <0.01 −60.93 18.09 <0.01 1.00 Significant increase
ʻŌʻmao 0.25 0.01 0.24 0.26 <0.01 −57.96 22.28 <0.01 1.00 Significant increase
Red-billed Leiothrix 0.03 0.01 0.02 0.03 <0.01 −29.77 −14.44 <0.01 <0.01 Negligible increase
Warbling White-eye −2.26 0.08 −2.39 −2.13 <0.01 27.45 −30.46 1.00 <0.01 Significant decrease
Yellow-fronted Canary A −2.10 0.02 −2.13 −2.07 <0.01 103.63 −109.02 1.00 <0.01 Significant decrease
Mauna Loa Strip ʻApapane −3.17 0.04 −3.23 −3.11 <0.01 80.90 −87.10 1.00 <0.01 Significant decrease
Eurasian Skylark A <−0.01 <0.01 <0.01 <0.01 <0.01 −453.90 −389.16 <0.01 <0.01 Negligible decrease
Hawaiʻi ʻAmakihi 0.37 0.06 0.28 0.47 <0.01 −9.03 4.85 <0.01 1.00 Significant increase
Hawaiʻi ʻElepaio −1.31 0.02 −1.35 −1.28 <0.01 50.21 −60.10 1.00 <0.01 Significant decrease
House Finch −0.03 <0.01 −0.03 −0.02 <0.01 −34.66 −43.02 <0.01 <0.01 Negligible decrease
ʻIʻiwi −0.76 0.01 −0.78 −0.74 <0.01 62.86 −86.16 1.00 <0.01 Significant decrease
Japanese Bush Warbler A 0.09 <0.01 0.08 0.09 <0.01 −93.38 25.82 <0.01 1.00 Significant increase
Northern Cardinal 0.14 <0.01 0.13 0.14 <0.01 −119.97 14.91 <0.01 1.00 Significant increase
ʻŌʻmao −0.12 <0.01 −0.12 −0.11 <0.01 −4.42 −62.98 <0.01 <0.01 Negligible decrease
Red-billed Leiothrix −0.07 0.02 −0.10 −0.04 <0.01 −3.73 −9.99 <0.01 <0.01 Negligible decrease
Warbling White-eye −2.45 0.05 −2.54 −2.36 <0.01 42.44 −46.70 1.00 <0.01 Significant decrease
Yellow-fronted Canary A 0.60 0.01 0.59 0.61 <0.01 −118.20 99.16 <0.01 1.00 Significant increase
Northwest Kahuku ʻApapane −1.80 0.01 −1.82 −1.77 <0.01 114.41 −130.41 1.00 <0.01 Significant decrease
Eurasian Skylark A −0.12 <0.01 −0.13 −0.12 <0.01 62.77 −165.88 1.00 <0.01 Significant decrease
Hawaiʻi ʻAmakihi −3.85 0.11 −4.03 −3.66 <0.01 33.18 −35.26 1.00 <0.01 Significant decrease
Hawaiʻi ʻElepaio −0.22 <0.01 −0.22 −0.21 <0.01 27.74 −103.55 1.00 <0.01 Significant decrease
House Finch 0.29 0.01 0.28 0.31 <0.01 −47.27 21.36 <0.01 1.00 Significant increase
ʻIʻiwi −0.02 <0.01 −0.02 −0.02 <0.01 −182.43 −197.29 <0.01 <0.01 Negligible decrease
Northern Cardinal 0.02 <0.01 0.02 0.02 <0.01 −104.01 −57.49 <0.01 <0.01 Negligible increase
ʻŌʻmao −0.20 <0.01 −0.21 −0.20 <0.01 28.17 −118.03 1.00 <0.01 Significant decrease
Warbling White-eye 0.02 0.01 0.01 0.04 <0.01 −22.82 −11.45 <0.01 <0.01 Negligible increase
Yellow-fronted Canary A −0.17 <0.01 −0.18 −0.17 <0.01 38.77 −75.49 1.00 <0.01 Significant decrease
ʻŌlaʻa ʻApapane −5.73 0.07 −5.85 −5.62 <0.01 79.66 −82.98 1.00 <0.01 Significant decrease
Hawaiʻi ʻAmakihi −0.07 <0.01 −0.07 −0.07 <0.01 −47.62 −129.67 <0.01 <0.01 Negligible decrease
Hawaiʻi ʻElepaio 0.45 0.02 0.42 0.48 <0.01 −31.05 18.56 <0.01 1.00 Significant increase
ʻIʻiwi −0.24 <0.01 −0.24 −0.23 <0.01 30.41 −98.39 1.00 <0.01 Significant decrease
Japanese Bush Warbler A 0.06 <0.01 0.05 0.07 <0.01 −25.50 2.98 <0.01 1.00 Significant increase
Northern Cardinal −0.45 0.01 −0.46 −0.44 <0.01 60.88 −105.24 1.00 <0.01 Significant decrease
ʻŌʻmao 0.32 0.01 0.31 0.33 <0.01 −72.09 34.60 <0.01 1.00 Significant increase
Red-billed Leiothrix 0.31 0.01 0.29 0.32 <0.01 −37.80 17.60 <0.01 1.00 Significant increase
Warbling White-eye −8.84 0.11 −9.03 −8.65 <0.01 76.30 −78.35 1.00 <0.01 Significant decrease
Yellow-fronted Canary A −0.02 <0.01 −0.02 −0.02 <0.01 −53.89 −93.06 <0.01 <0.01 Negligible decrease
Pāpā ʻApapane 0.46 0.10 0.29 0.62 <0.01 −5.88 3.55 <0.01 1.00 Significant increase
Eurasian Skylark A −0.02 <0.01 −0.02 −0.02 <0.01 −82.62 −153.87 <0.01 <0.01 Negligible decrease
Hawaiʻi ʻAmakihi −7.46 0.15 −7.71 −7.21 <0.01 48.49 −50.03 1.00 <0.01 Significant decrease
Hawaiʻi ʻElepaio 0.38 0.01 0.37 0.40 <0.01 −54.30 29.56 <0.01 1.00 Significant increase
House Finch −0.65 0.01 −0.67 −0.63 <0.01 46.63 −67.59 1.00 <0.01 Significant decrease
ʻIʻiwi −0.16 0.01 −0.17 −0.15 <0.01 4.43 −45.63 1.00 <0.01 Significant decrease
Japanese Bush Warbler A 0.07 <0.01 0.06 0.07 <0.01 −76.13 12.71 <0.01 1.00 Significant increase
Northern Cardinal 0.22 <0.01 0.21 0.22 <0.01 −81.42 26.83 <0.01 1.00 Significant increase
ʻŌʻmao −0.81 0.02 −0.84 −0.79 <0.01 42.40 −56.85 1.00 <0.01 Significant decrease
Red-billed Leiothrix 0.47 0.02 0.44 0.50 <0.01 −36.61 22.42 <0.01 1.00 Significant increase
Warbling White-eye −0.56 0.01 −0.58 −0.54 <0.01 38.25 −59.18 1.00 <0.01 Significant decrease
Yellow-fronted Canary A −1.80 0.02 −1.83 −1.76 <0.01 80.85 −85.78 1.00 <0.01 Significant decrease

A Species assessed using 2020–2021 and 2015–2016 data, as it was not detected in 2010.

B Density changes were interpreted as significant increase (also with green background), significant decrease (also with orange background), negligible increase, or negligible decrease (with “negligible” referring to statistically significant but small differences, with no background color).

The largest decrease in density among natives was for ʻApapane in the East Rift Zone tract, with a decrease of −11.81 ± 0.14 birds/ha (Table 4). In the same tract, Hawaiʻi ʻAmakihi and ’Ōma’o also significantly decreased. ʻApapane, Hawaiʻi ʻElepaio, and ʻIʻiwi showed decreases in the Mauna Loa Strip tract. In the Northwest Kahuku tract, densities of every native species detected in 2010 have since decreased; ʻIʻiwi were not detected in 2016 or 2021, resulting in a significant decrease. In the ʻŌlaʻa tract, ʻApapane significantly decreased by −5.73 ± 0.07 birds/ha, and ʻIʻiwi, already rare, were not detected in 2020. In the Pāpā tract, Hawaiʻi ʻAmakihi significantly decreased by −7.46 ± 0.15 birds/ha, while both ʻIʻiwi and ’Ōma’o were not detected in 2021.

For non-native species, the largest increase was for the Warbling White-eye in the East Rift Zone tract, which increased by +7.35 ± 0.16 birds/ha (Table 4). The next largest increase was for the Red-billed Leiothrix in the Honomalino tract (+0.72 ± 0.01 birds/ha), and this species also increased in the ʻŌlaʻa and Pāpā tracts. Japanese Bush Warbler densities increased in every tract except in the Mauna Loa South Flank, where there was a negligible decrease, and Northwest Kahuku, where the species has not been detected. Northern Cardinal densities increased in every tract except ʻŌlaʻa, where they decreased by −0.45 ± 0.01 birds/ha. The largest decrease among non-natives was of the Warbling White-eye in the ʻŌlaʻa tract (−8.84 ± 0.11 birds/ha), with additional decreases in Honomalino, Mauna Loa South Flank, Mauna Loa Strip, and Pāpā tracts. Differences were mixed for the Yellow-fronted Canary, showing decreases in the Honomalino, Mauna Loa South Flank, and Pāpā tracts, increases in the East Rift Zone and Mauna Loa Strip tracts, and negligible change in the ʻŌlaʻa tract. Differences were mixed for the remaining non-native species and will be discussed further in the species summaries.

Species Summaries

Below, a summary is provided for each species detected during the 2020–2021 HAVO landbird survey. For all species, occurrence is collocated with vegetation classifications described and mapped by Green et al. (2015). In areas where vegetation classifications (capitalized) were unavailable, habitat data collected by surveyors in 2020 and 2021 (described below in the “2020–2021 Habitat Results” section) were used to characterize habitat types (not capitalized) in which birds were detected. Occurrence maps in the Appendix display detections of each species within both the Kahuku Unit and Old HAVO.

African Silverbill

There were six African Silverbill (Euodice cantans) detections. The detections were all within the Mauna Loa South Flank tract (Appendix), where it occurred at 8.5% of the stations surveyed for an average of 0.13 BPC. The detections were in ʻŌhi’a / Kikuyu Grass Semi-natural Woodland.

American Barn Owl

A single American Barn Owl (Tyto furcata) was detected at one station in the Mauna Loa Strip tract (Appendix). The non-native raptor was seen near 1,500 m elevation, in Koa / Non-native Grass Semi-natural Woodland. A nocturnal hunter, the individual was likely spooked from its daytime roost by the surveyor.

ʻApapane

There were 1,876 ʻApapane detections. This species was the most widely distributed landbird detected, occurring at 87.1% of the 450 stations surveyed and across most habitat types, except for unvegetated lava and open grasslands (Appendix). ʻApapane occurred at all stations surveyed in the Honomalino and Pāpā tracts, with averages of 7.10 BPC and 6.09 BPC, respectively.

In 2021, ʻApapane density was highest in the Honomalino tract, corresponding to an abundance of 30,812 ± 94 birds (Table 5). Densities in the Honomalino, Pāpā, and Mauna Loa South Flank tracts were significantly higher in 2021 than in 2010. In contrast, densities were lower in the Northwest Kahuku tract and across all three Old HAVO tracts relative to 2010.

Table 5. ʻApapane density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
East Rift Zone 2010 24.25 ± 0.13
(18–34)		 54,652 ± 286
(40,923–76,049)
2015 24.00 ± 0.07
(20–29)		 42,744 ± 133
(35,671–51,812)
2020 12.43 ± 0.06
(10–16)		 22,143 ± 99
(16,951–28,950)
Honomalino 15.52 ± 0.05
(13–19)		 26,196 ± 85
(22,138–32,087)
2016 19.91 ± 0.07
(16–25)		 33,607 ± 116
(27,449–41,644)
2021 18.25 ± 0.06
(15–22)		 30,812 ± 94
(25,473–37,180)
Mauna Loa South Flank 2010 7.09 ± 0.04
(5–10)		 32,556 ± 168
(23,899–44,815)
2016 6.71 ± 0.03
(5–9)		 30,812 ± 148
(22,806–41,915)
2021 10.20 ± 0.05
(8–14)		 46,830 ± 218
(35,762–62,093)
Mauna Loa Strip 2010 8.22 ± 0.03
(7–10)		 26,151 ± 103
(20,705–33,362)
2015 13.13 ± 0.06
(10–17)		 41,766 ± 176
(31,985–54,386)
2020 5.05 ± 0.02
(4–6)		 16,058 ± 60
(12,592–20,039)
Northwest Kahuku 2010 2.58 ± 0.01
(2–3)		 2,284 ± 12
(1,657–3,067)
2016 2.69 ± 0.01
(2–4)		 2,376 ± 11
(1,739–3,144)
2021 0.79 ± 0.01
(0–1)		 695 ± 6
(396–1,091)
ʻŌlaʻa 2010 18.26 ± 0.06
(15–22)		 44,672 ± 144
(36,562–53,698)
2015 28.88 ± 0.08
(24–34)		 70,652 ± 190
(59,822–83,725)
2020 12.53 ± 0.04
(10–15)		 30,652 ± 95
(25,244–36,954)
Pāpā 2010 8.88 ± 0.06
(6–14)		 2,923 ± 21
(2,022–4,484)
2016 9.75 ± 0.06
(7–15)		 3,208 ± 21
(2,266–4,805)
2021 9.34 ± 0.08
(6–16)		 3,073 ± 25
(2,111–5,258)

Occurrence of ʻApapane was lowest in the Northwest Kahuku tract, where the species was detected at 47.2% of stations surveyed for an average of 0.87 BPC. The 2021 density estimate in this tract was 0.79 ± 0.01 birds/ha, corresponding to an estimated abundance of 695 ± 6 birds, representing a significant decline since 2010. Decreasing densities were also observed in the East Rift Zone, Mauna Loa Strip, and ʻŌlaʻa tracts. The most pronounced decrease in estimates occurred in the Mauna Loa Strip tract, where abundance decreased by nearly 62% since 2015.

California Quail

There were 38 detections of the California Quail (Callipepla californica). The game bird occurred at 26.4% (0.43 BPC) of the stations surveyed in the Northwest Kahuku tract and at 4.4% (0.07 BPC) of stations in the Mauna Loa Strip tract (Appendix). Detections were near sub-alpine lava flows near 2,000 m elevation in the Mauna Loa Strip tract and as high as 2,400 m elevation in the Northwest Kahuku tract, in mixed bare ground and non-native grasses understory.

Chinese Hwamei

There were 24 Chinese Hwamei (Garrulax canorus) detections. The species occurred at 15.4% (0.19 BPC) of the stations surveyed in the Mauna Loa Strip tract and at 12.7% (0.13 BPC) of stations in the East Rift Zone tract (Appendix). Detections were broadly distributed above 1,500 m elevation in Pūkiawe – ’A’ali’i Montane Shrubland and Koa – Pūkiawe Montane Woodland within the Mauna Loa Strip tract. In the East Rift Zone tract, detections were between 800 m and 900 m elevation, in ʻōhi’a and hāpuʻu dominated canopy, with uluhe dominated understory.

Common Myna

Two Common Myna (Acridotheres tristis) were detected, one of which was in the Mauna Loa Strip tract (1.1% occurrence; 0.01 BPC), in Pūkiawe – ’A’ali’i Montane Shrubland near 1,500 m elevation (Appendix). The other detection was in the ʻŌlaʻa tract (1.1% occurrence; 0.01 BPC), in ’Ōhi’a – ’Ōlapa / (Hāpuʻu spp.) Montane Wet Forest near the park boundary and privately owned pastureland.

Common Waxbill

There were 20 Common Waxbill (Estrilda astrild) detections. The species occurred at 4.4% (0.10 BPC) of the stations surveyed in the Mauna Loa Strip tract and at 8.5% (0.23 BPC) of stations in the Mauna Loa South Flank tract (Appendix). Detections in the Mauna Loa Strip tract were above 1,500 m elevation in Pūkiawe – ’A’ali’i Montane Shrubland. Detections in the Mauna Loa South Flank ranged from 800 m to 1,200 m elevation in ’Ōhi’a / Kikuyu Grass Semi-natural Woodland.

Erckel’s Spurfowl

There were 259 detections of the Erckel’s Spurfowl. The game bird occurred in the Honomalino, Mauna Loa South Flank, Northwest Kahuku, and Pāpā tracts. The highest occurrence was within the Northwest Kahuku and Mauna Loa Strip tracts (Appendix), where it occurred at 69.4% (1.61 BPC) and 56% (0.85 BPC) of stations surveyed, respectively. The lowest detection was near 1,500 m elevation in Honomalino, in ’Ōhi’a / Meadow Ricegrass Semi-natural Woodland, while the highest detection was near the 2,400 m contour in the Northwest Kahuku tract, in ’Ōhi’a / Pūkiawe – ’A’ali’i Montane Woodland and unvegetated lava.

Eurasian Skylark

There were 21 detections of the Eurasian Skylark. There was a single detection in the Mauna Loa Strip tract, while the remaining detections were in the Northwest Kahuku tract (Appendix), where it occurred at 22.2% of the stations surveyed for an average of 0.27 BPC. Most detections were in Māmane Montane Sparse Vegetation or Māmane / Meadow Ricegrass Subalpine Semi-natural Woodland. Detections in 2015 and 2016 allowed for a population change assessment in the Mauna Loa South Flank, Mauna Loa Strip, Northwest Kahuku, and Pāpā tracts. In 2021, there was an estimated abundance of 31 ± 1 birds in the Northwest Kahuku tract, which was a significant decrease in density from its 2016 abundance of 141 ± 1 birds (Table 6). The decreased differences in density were negligible in the three remaining tracts.

Table 6. Eurasian Skylark density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
Mauna Loa South Flank 2010 – –
2016 0.01 ± <0.01
(0–0.03)		 54 ± 1
(8–124)
2021 – –
Mauna Loa Strip 2010 – –
2015 <0.01 ± <0.01
(0–<0.01)		 14 ± 1
(0–40)
2020 <0.01 ± <0.01
(0–<0.01)		 5.89 ± 0.22
(0–24)
Northwest Kahuku 2010 – –
2016 0.16 ± <0.01
(0.1–0.06)		 141 ± 1
(96–200)
2021 0.04 ± <0.01
(0.02–0.07)		 31 ± 1
(15–56)
Pāpā 2010 – –
2016 0.02 ± <0.01
(0–0.06)		 7 ± 1
(0–19)
2021 – –

Hawaiʻi ʻAmakihi

There were 1,411 total detections of the Hawaiʻi ʻAmakihi. It was the second most detected species, occurring at 83.8% of total stations surveyed at an average of 3.11 BPC. Occurrence and BPC were highest in the Mauna Loa Strip, Honomalino, Mauna Loa South Flank, and Northwest Kahuku tracts (Appendix). Detections occurred broadly among vegetation classifications, including ʻŌhi’a / Pūkiawe – ʻAʻaliʻi Montane Woodland, ʻŌhi’a / Kikuyu Grass (Cenchrus clandestinus) Semi-natural Woodland, Koa / Non-native Grass Semi-natural Woodland, and Pūkiawe – ’A’ali’i Montane Shrubland.

The population density was highest in the Honomalino tract, with an estimated 22.63 ± 0.08 birds/ha, for an estimated abundance of 38,203 ± 140 birds, which was a significant decrease since 2010 (Table 7). The estimated density in the Northwest Kahuku tract of 19.71 ± 0.07 birds/ha was the next highest, but a significant decrease since 2010. In contrast, the estimated density of 11.09 ± 0.05 birds/ha in the Mauna Loa South Flank tract, corresponding to an abundance of 50,917 ± 214 birds, was a significant increase since 2010. However, the 2021 estimate was 43% lower than the 2016 estimate of 19.56 ± 0.06 birds/ha. This scenario similarly occurred in the Mauna Loa Strip, where the 2020 estimate was significantly higher than 2010, but was 55% lower than the 2015 estimate of 15.07 birds/ha. The 2021 density of 10.49 ± 0.10 birds/ha in the Pāpā tract was a significant decrease.

Table 7. Hawaiʻi ʻAmakihi density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
East Rift Zone 2010 0.19 ± 0.01
(0–0.58)		 431 ± 11
(0–1,300)
2015 0.30 ± <0.01
(0–0.56)		 526 ± 7
(172–995)
2020 0.11 ± <0.01
(0–0.37)		 188 ± 6
(0–653)
Honomalino 2010 23.98 ± 0.08
(19.82–29.71)		 40,485 ± 136
(33,451–50,159)
2016 22.74 ± 0.07
(19.08–28.10)		 38,389 ± 125
(32,199–47,431)
2021 22.63 ± 0.08
(18.46–28.82)		 38,203 ± 140
(31,153–48,647)
Mauna Loa South Flank 2010 10.58 ± 0.04
(8.73–13.30)		 48,609 ± 169
(40,082–61,075)
2016 19.56 ± 0.06
(16.64–23.51)		 89,830 ± 257
(76,407–107,997)
2021 11.09 ± 0.05
(8.81–14.35)		 50,917 ± 214
(40,482–65,887)
Mauna Loa Strip 2010 9.34 ± 0.04
(7.36–12.09)		 29,716 ± 119
(23,406–38,445)
2015 15.07 ± 0.06
(12.11–19.20)		 47,942 ± 184
(38,523–61,080)
2020 9.72 ± 0.04
(7.62–12.81)		 30,904 ± 132
(24,248–40,764)
Northwest Kahuku 2010 23.55 ± 0.09
(19.22–29.59)		 20,823 ± 75
(16,993–26,158)
2016 23.03 ± 0.07
(18.85–27.89)		 20,359 ± 65
(16,660–24,657)
2021 19.71 ± 0.07
(15.94–24.64)		 17,420 ± 64
(14,092–21,779)
ʻŌlaʻa 2010 0.07 ± <0.01
(0–0.16)		 167 ± 3
(0–401)
2015 0.02 ± <0.01
(0–0.08)		 53 ± 2
(0–198)
2020 – –
Pāpā 2010 17.95 ± 0.12
(12.46–26.45)		 5,906 ± 38
(4,100–8,701)
2016 13.85 ± 0.10
(9.63–21.1)		 4,558 ± 32
(3,170–6,942)
2021 10.49 ± 0.10
(5.82–17.90)		 3,452 ± 31
(1,915–5,888)

The species was mostly absent from the ʻŌhi’a / Hāpuʻu spp. (Cibotium spp.) Montane Wet Forest of the East Rift Zone tract, where there were only three detections at one station (1.8% occurrence; 0.05 BPC). The 2020 density in the East Rift Zone tract was 0.11 ± <0.01 birds/ha for an estimated abundance of 188 ± 6 birds (Table 7). Hawaiʻi ʻAmakihi were not detected in the ʻŌhi’a – ʻŌlapa / (Hāpuʻu spp.) Montane Wet Forest of the ʻŌlaʻa tract, resulting in undetermined abundance in 2020, where there were 167 ± 3 birds in 2010. Differences in density were negligible in both the ʻŌlaʻa and East Rift Zone tracts, where densities have remained low (<0.5 birds/ha) across all survey years.

Hawaiʻi ʻElepaio

There were 171 total detections of the Hawaiʻi ʻElepaio. The species occurred at 19.1% of total stations surveyed at an average 0.38 BPC. Occurrence and BPC were highest in the Honomalino (53.2% occurrence; 1.37 BPC), Mauna Loa Strip (28.6% occurrence; 0.44 BPC), and ʻŌlaʻa (14.7% occurrence; 0.20 BPC) tracts, in Koa / Non-native Grass, ’Ōhi’a / Meadow Ricegrass Semi-natural Woodland, and ’Ōhi’a – ’Ōlapa / (Hāpuʻu spp.) Montane Wet Forest. There was a single detection in the Northwest Kahuku tract (1.1% occurrence; 0.01 BPC), in Māmane Subalpine Woodland. There was also a single detection in the Mauna Loa South Flank tract (1.1% occurrence; 0.01 BPC), in ʻŌhi’a / Kikuyu Grass Semi-natural Woodland. The species was not detected in the East Rift Zone tract (Appendix).

The population density was highest in the Honomalino tract, with an estimated 8.99 ± 0.11 birds/ha and an abundance of 15,178 ± 179 birds, representing a significant increase since 2010 when the density was 0.62 ± 0.02 birds/ha and the abundance was 1,047 ± 27 birds (Table 8). The next highest density was in the Mauna Loa Strip tract, with 0.85 ± 0.01 birds/ha. This tract had an abundance of 2,701 ± 34 birds, which was a significant decrease since 2010. In the ʻŌlaʻa tract, densities more than doubled to a 2020 abundance of 2,041 ± 39 birds. After no birds were detected in the Pāpā tract in 2010 or 2016, there was a significant increase after just two detections in 2021, resulting in an abundance of 125 ± 3 birds (Table 8).

Table 8. Hawaiʻi ʻElepaio density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
Honomalino 2010 0.62 ± 0.02
(0–2.07)		 1,047 ± 27
(102–3,496)
2016 2.02 ± 0.03
(0.77–4.79)		 3,415 ± 56
(1,302–8,077)
2021 8.99 ± 0.11
(4.61–17.64)		 15,178 ± 179
(7,788–29,778)
Mauna Loa Strip 2010 2.16 ± 0.02
(1.32–3.92)		 6,884 ± 67
(4,204–12,469)
2015 2.04 ± 0.04
(0.75–5.67)		 6,494 ± 131
(2,370–18,026)
2020 0.85 ± 0.01
(0.41–1.73)		 2,701 ± 34
(1,320–5,504)
Northwest Kahuku 2010 0.25 ± <0.01
(0.09–0.44)		 219 ± 3
(83–392)
2016 0.22 ± 0.01
(0–1.06)		 197 ± 8
(0–937)
2021 0.03 ± <0.01
(0–0.10)		 27 ± 1
(0–92)
ʻŌlaʻa 2010 0.39 ± 0.01
(0.08–1.22)		 944 ± 23
(189–2,989)
2015 0.39 ± 0.01
(0.05–1.30)		 952 ± 25
(128–3,200)
2020 0.83 ± 0.02
(0.27–2.15)		 2,041 ± 39
(669–5,271)
Pāpā 2010 – –
2016 – –
2021 0.38 ± 0.01
(0–1.15)		 125 ± 3
(0–379)

House Finch

There were 225 House Finch detections. The species occurred at 23.8% of total stations surveyed at an average 0.48 BPC. Its distribution was greatest in the Northwest Kahuku tract (Appendix), where it occurred at 86.1% of stations surveyed at an average of 1.97 BPC. Detections were in a variety of vegetation classifications, including Māmane / Meadow Ricegrass Subalpine Semi-natural Woodland, Pūkiawe – ’A’ali’i Montane Shrubland, and ’Ōhi’a / (Pūkiawe – ’A’ali’i) Montane Sparse Vegetation. There were 31 detections in the Mauna Loa South Flank tract (36.2% occurrence; 0.66 BPC), where the species was detected primarily in ʻŌhi’a / Kikuyu Grass Semi-natural Woodland. There were 21 detections in the Mauna Loa Strip tract (15.4% occurrence; 0.23 BPC), where the species occurred in a mix of vegetation classes, including Koa / Non-native Grass Semi-natural Woodland, Pūkiawe – ’A’ali’i Montane Shrubland, Koa / Pūkiawe Montane Woodland, and Pūkiawe – ’A’ali’i Montane Sparse Vegetation. Indices were roughly similar in the Honomalino tract (17.7% occurrence; 0.32 BPC), where it was detected in ʻŌhi’a / Pūkiawe – ʻAʻaliʻi Montane Woodland and ʻŌhi’a / Meadow Ricegrass Semi-natural Woodland.

The species exhibited increases in density in the Northwest Kahuku tract since 2010, increasing to a 2021 estimate of 1.04 ± 0.01 birds/ha and an abundance of 915 ± 5 birds (Table 9). Densities were significantly lower in the Mauna Loa Strip, Honomalino, and Mauna Loa South Flank tracts. The House Finch was not detected in the East Rift Zone or ʻŌlaʻa tracts in 2010, 2015, or 2020. No birds were detected in the Pāpā tract either, but the species was detected there in both 2010 and 2016; thus, there was a significant decrease in density since 2016, when we estimated an abundance of 287 ± 4 birds.

Table 9. House Finch density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
Honomalino 2010 1.84 ± 0.02
(0.86–3.25)		 3,101 ± 33
(1,447–5,478)
2016 0.66 ± 0.01
(0.27–1.31)		 1,111 ± 15
(460–2,208)
2021 0.19 ± <0.01
(0.09–0.37)		 325 ± 4
(151–619)
Mauna Loa South Flank 2010 2.77 ± 0.02
(1.79–4.07)		 12,734 ± 85
(8,237–18,684)
2016 1.72 ± 0.01
(1.18–2.47)		 7,921 ± 49
(5,418–11,354)
2021 0.40 ± <0.01
(0.20–0.74)		 1,838 ± 20
(901–3,394)
Mauna Loa Strip 2010 0.15 ± <0.01
(0.03–0.34)		 462 ± 8
(93–1,077)
2015 0.24 ± <0.01
(0.09–0.42)		 755 ± 9
(283–1,347)
2020 0.12 ± <0.01
(0.05–0.23)		 376 ± 5
(151–747)
Northwest Kahuku 2010 0.74 ± 0.01
(0.38–1.23)		 655 ± 6
(340–1,088)
2016 1.52 ± 0.01
(1.14–2.05)		 1,343 ± 6
(1,006–1,811)
2021 1.04 ± 0.01
(0.73–1.45)		 915 ± 5
(646–1,284)
Pāpā 2010 0.65 ± 0.01
(0.11–1.51)		 214 ± 4
(37–497)
2016 0.87 ± 0.01
(0.29–1.90)		 287 ± 4
(95–626)
2021 – –

ʻIʻiwi

There were 19 detections of ʻIʻiwi, all of which were within the Honomalino tract (Appendix), where it occurred at 13.9% of the stations surveyed at an average of 0.24 BPC. The detections were above 1,400 m elevation and only within the TNC portion of the tract, in ’ōhi’a and koa dominated canopy with an understory of native shrubs and non-native grasses. The species showed an increased density in the Honomalino tract since 2010, increasing to a 2021 estimate of 0.81 ± 0.02 birds/ha and an abundance of 1,366 ± 26 birds (Table 10). In prior years, ʻIʻiwi were detected in the Mauna Loa Strip, Northwest Kahuku, ʻŌlaʻa, and Pāpā tracts, but since the species was not detected in any of these tracts in 2020 or 2021, there was an undetermined abundance for each tract and either a negligible or significant decrease in densities.

Table 10. ʻIʻiwi density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
Honomalino 2010 0.64 ± 0.01
(0.19–1.36)		 1,074 ± 16
(326–2,301)
2016 0.65 ± 0.01
(0.27–1.34)		 1,098 ± 15
(452–2,268)
2021 0.81 ± 0.02
(0.15–1.96)		 1,366 ± 26
(258–3,306)
Mauna Loa Strip 2010 0.76 ± 0.01
(0.30–1.56)		 2,417 ± 32
(952–4,969)
2015 0.09 ± <0.01
(0– <0.01)		 280 ± 5
(0–688)
2020 – –
Northwest Kahuku 2010 0.02 ± <0.01
(0–0.06)		 17 ± 1
(0–57)
2016 – –
2021 – –
ʻŌlaʻa 2010 0.24 ± <0.01
(0.06–0.50)		 575 ± 8
(153–1,226)
2015 0.27 ± 0.01
(0.04–0.84)		 656 ± 16
(95–2,046)
2020 – –
Pāpā 2010 0.16 ± 0.01
(0–0.62)		 51 ± 2
(0–205)
2016 1.95 ± 0.03
(0.62–4.14)		 640 ± 10
(205–1,362)
2021 – –

ʻIo

There were 10 detections of the ʻIo. There were five detections on four stations in the Mauna Loa South Flank tract (Appendix), where the hawk occurred at 8.5% of stations surveyed for an average of 0.11 BPC. Detections were in ’Ōhi’a / Kikuyu Grass Semi-natural Woodland and Koa / ’Ōhi’a Montane Dry Woodland. There were five detections on five stations in the ʻŌlaʻa tract, where it occurred at 5.3% of stations surveyed at 0.05 BPC. The detections in the ʻŌlaʻa tract were within ’Ōhi’a – ’Ōlapa / (Hāpuʻu spp.) Montane Wet Forest.

Japanese Bush Warbler

There were 254 Japanese Bush Warbler detections; the species occurred at 28.4% of total stations surveyed at an average 0.56 BPC. It was most widespread in the East Rift Zone tract (Appendix), particularly in ’Ōhi’a / Hāpuʻu spp. Montane Wet Forest, where it occurred at 70.9% of stations surveyed at an average of 1.77 BPC. Density increased in the East Rift Zone tract to a 2021 estimate of 1.19 ± <0.01 birds/ha and an abundance of 2,118 ± 11 birds (Table 11). The Japanese Bush Warbler was not detected in any tract in 2010, but was detected in all tracts except Northwest Kahuku during the 2015–2016 and 2020–2021 surveys. There was an irruption in the ʻŌlaʻa tract, where the species increased from an undetermined density in 2010 to a 2020 density of 0.66 ± <0.01 birds/ha and an abundance of 1,602 ± 8 birds. Significant increases also occurred in the Honomalino, Mauna Loa Strip, and Pāpā tracts, where occurrence was highest in ’ōhi’a and koa dominated canopy, with an understory of native shrubs and non-native grasses. Differences in the Mauna Loa South Flank were negligible after the species had an estimated abundance of 200 ± 3 birds in 2016, but then it was not detected in 2021.

Table 11. Japanese Bush Warbler density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
East Rift Zone 2010 – –
2015 0.97 ± <0.01
(0.73–1.29)		 1,720 ± 8
(1,291–2,298)
2020 1.19 ± <0.01
(0.88–1.63)		 2,118 ± 11
(1,564–2,902)
Honomalino 2010 – –
2016 0.06 ± <0.01
(0.02–0.11)		 94 ± 1
(34–184)
2021 0.32 ± <0.01
(0.19–0.51)		 534 ± 4
(321–859)
Mauna Loa South Flank 2010 – –
2016 0.04 ± <0.01
(0.01–0.09)		 200 ± 3
(47–425)
2021 – –
Mauna Loa Strip 2010 – –
2015 0.06 ± <0.01
(0.02–0.12)		 183 ± 2
(67–369)
2020 0.14 ± <0.01
(0.07–0.24)		 460 ± 4
(232–771)
ʻŌlaʻa 2010 – –
2015 0.59 ± <0.01
(0.42–0.81)		 1,454 ± 8
(1,031–1,993)
2020 0.66 ± <0.01
(0.48–0.89)		 1,602 ± 8
(1,162–2,166)
Pāpā 2010 – –
2016 – –
2021 0.07 ± <0.01
(0–0.19)		 22 ± 1
(0–63)

Kalij Pheasant

There were 16 Kalij Pheasant (Lophura leucomelanos) detections; the species occurred at 2.7% of the total stations surveyed, for an average of 0.03 BPC. The detections were in the Honomalino (5.1% occurrence; 0.06 BPC), Mauna Loa Strip (2.2% occurrence; 0.05 BPC), Mauna Loa South Flank (8.5% occurrence; 0.09 BPC), and Northwest Kahuku (2.8% occurrence; 0.03 BPC) tracts (Appendix). Detections were in a mix of vegetation classes, such as ’Ōhi’a / Kikuyu Grass Semi-natural Woodland, ’Ōhi’a / Sword Fern Semi-natural Woodland, Koa / (’Ōhi’a) / Meadow Ricegrass Semi-natural Montane Mesic Woodland, and Pūkiawe – ’A’ali’i Montane Shrubland.

Nēnē

A total of seven Nēnē were detected. The detections were on two stations in the Mauna Loa South Flank tract (Appendix), where it occurred at 4.3% of stations surveyed for an average of 0.15 BPC. The stations were above 1,400 m elevation in Koa / ’Ōhi’a Montane Dry Woodland.

Northern Cardinal

There were 304 Northern Cardinal detections; the species occurred at 44.0% of total stations surveyed at an average 0.67 BPC. Its distribution was greatest in the Honomalino tract (Appendix), where it occurred at 72.2% of stations surveyed at 1.18 BPC. In 2021, density in this tract was 0.89 ± <0.01 birds/ha, corresponding to an abundance of 1,505 ± 7 birds—a significant increase since 2010 (Table 12). Density also increased in the East Rift Zone tract, reaching 0.38 ± <0.01 birds/ha in 2021 for an abundance of 681 ± 7 birds. Significant increases were detected in every tract where the species occurred except Northwest Kahuku, where the increase was negligible (Table 12). In the Pāpā tract, density rose significantly since 2010 but the 2021 estimate was 64% lower than the 2016 peak of 0.80 ± 0.01 birds/ha. The species occurred in a variety of vegetation classes, including ’Ōhi’a / Pūkiawe – ’A’ali’i Montane Woodland, ’Ōhi’a / Meadow Ricegrass Semi-natural Woodland, ’Ōhi’a / Hāpuʻu spp. Montane Wet Forest, and Koa / Non-native Grass.

Table 12. Northern Cardinal density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
East Rift Zone 2010 0.13 ± <0.01
(0–0.41)		 295 ± 8
(0–932)
2015 0.55 ± <0.01
(0.34–0.86)		 975 ± 8
(605–1,538)
2021 0.38 ± <0.01
(0.17–0.67)		 681 ± 7
(309–1,191)
Honomalino 2010 0.58 ± <0.01
(0.38–0.84)		 982 ± 6
(638–1,420)
2016 0.72 ± <0.01
(0.53–0.95)		 1,221 ± 6
(891–1,611)
2021 0.89 ± <0.01
(0.67–1.19)		 1,505 ± 7
(1,129–2,011)
Mauna Loa South Flank 2010 0.59 ± <0.01
(0.42–0.79)		 2,689 ± 14
(1,932–3,617)
2016 0.34 ± <0.01
(0.22–0.49)		 1,552 ± 10
(1,011–2,238)
2021 0.79 ± <0.01
(0.54–1.09)		 3,611 ± 21
(2,463–4,987)
Mauna Loa Strip 2010 0.14 ± <0.01
(0.07–0.25)		 452 ± 4
(223–793)
2015 0.68 ± <0.01
(0.50–0.89)		 2,150 ± 10
(1,598–2,846)
2021 0.28 ± <0.01
(0.18–0.40)		 883 ± 5
(586–1,257)
Northwest Kahuku 2010 0.09 ± <0.01
(0.05–0.14)		 76 ± 1
(43–125)
2016 0.12 ± <0.01
(0.06–0.19)		 105 ± 1
(54–171)
2021 0.10 ± <0.01
(0.04–0.19)		 93 ± 1
(36–172)
ʻŌlaʻa 2010 0.75 ± <0.01
(0.50–1.09)		 1,842 ± 12
(1,232–2,660)
2015 0.81 ± <0.01
(0.55–1.15)		 1,975 ± 12
(1,347–2,824)
2021 0.30 ± <0.01
(0.20–0.47)		 739 ± 5
(478–1,141)
Pāpā 2010 0.07 ± <0.01
(0–0.29)		 25 ± 1
(0–96)
2016 0.80 ± 0.01
(0.48–1.33)		 264 ± 2
(159–436)
2021 0.29 ± <0.01
(0.16–0.54)		 96 ± 1
(53–177)

Northern Mockingbird

There were 44 Northern Mockingbird (Mimus polyglottos) detections, all of which were in the Northwest Kahuku tract (Appendix), where the species occurred at 47.2% of the stations surveyed at 0.59 BPC. Detections were in a mix of Māmane / Meadow Ricegrass Subalpine Semi-natural Woodland, Māmane Montane Sparse Vegetation, and Naio Subalpine Woodland.

’Ōma’o

There were 187 detections of ’Ōma’o, with the species occurring at 25.8% of stations surveyed at 0.41 BPC. Its distribution was greatest in the East Rift Zone tract (Appendix), where it occurred at 70.9% of stations surveyed at 1.25 BPC, primarily in ’Ōhi’a / Uluhe Lowland Mesic Woodland and Uluhe Wet Herbaceous Mat. Density in this tract increased significantly since 2010, reaching 1.96 ± 0.01 birds/ha in 2020 for an abundance of 3,494 ± 16 birds (Table 13). In the Mauna Loa Strip tract, ʻŌmaʻo occurred at 36.3% of stations surveyed at 0.49 BPC, with detections concentrated above 1,700 m elevation in Koa / Pūkiawe–(ʻAʻaliʻi) Montane Woodland and Pūkiawe–ʻAʻaliʻi Montane Shrubland. Density in 2020 was estimated at 0.21 ± <0.01 birds/ha, with an abundance of 668 ± 7 birds, representing a negligible change relative to 2010. In the ʻŌlaʻa tract, ʻŌmaʻo occurred at 24.2% of stations surveyed at an average of 0.43 BPC. Detections were primarily within ʻŌhiʻa–ʻŌlapa / (Hāpuʻu spp.) Montane Wet Forest, ʻŌhiʻa / Hāpuʻu spp. Montane Wet Forest, and Koa / Hāpuʻu spp. Montane Woodland. Density in 2020 was estimated at 0.69 ± 0.01 birds/ha, with an abundance of 1,682 ± 13 birds. Although this represented a significant increase relative to 2010, density was approximately 25% lower than the 2015 estimate. In the Mauna Loa South Flank tract, ʻŌmaʻo occurred at 44.7% of stations surveyed in 2021 at 0.64 BPC, primarily within ʻŌhiʻa / Kikuyu Grass Semi-natural Woodland and Koa / ʻŌhiʻa Montane Dry Woodland. Density in 2021 was estimated at 0.66 ± 0.01 birds/ha, corresponding to an abundance of 3,035 ± 23 birds. This represented a significant increase relative to 2010 but was approximately 25% lower than the 2015 estimate. ʻŌmaʻo were not detected in any leeward tracts during recent surveys, resulting in significant decreases in the Northwest Kahuku and Pāpā tracts relative to 2010. In the Honomalino tract, detections were insufficient to estimate density in either 2010 or 2016, and there were no detections in 2021.

Table 13. ’Ōma’o density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
East Rift Zone 2010 2.66 ± 0.02
(1.89–3.76)		 6,000 ± 34
(4,268–8,483)
2015 1.32 ± 0.01
(0.94–1.80)		 2,355 ± 12
(1,671–3,204)
2020 1.96 ± 0.01
(1.50–2.60)		 3,494 ± 16
(2,668–4,632)
Mauna Loa South Flank 2010 0.41 ± <0.01
(0.21–0.70)		 1,896 ± 19
(944–3,234)
2016 0.57 ± <0.01
(0.37–0.84)		 2,624 ± 18
(1,691–3,840)
2021 0.66 ± 0.01
(0.41–1.04)		 3,035 ± 23
(1,871–4,789)
Mauna Loa Strip 2010 0.33 ± <0.01
(0.18–0.52)		 1,035 ± 9
(576–1,665)
2015 0.53 ± <0.01
(0.31–0.79)		 1,682 ± 12
(999–2,503)
2020 0.21 ± <0.01
(0.10–0.37)		 668 ± 7
(326–1,168)
Northwest Kahuku 2010 0.20 ± <0.01
(0.08–0.40)		 180 ± 2
(69–355)
2016 – –
2021 – –
ʻŌlaʻa 2010 0.37 ± <0.01
(0.19–0.62)		 905 ± 9
(455–1,524)
2015 0.92 ± 0.01
(0.57–1.43)		 2,251 ± 17
(1,390–3,496)
2020 0.69 ± 0.01
(0.42–1.05)		 1,682 ± 13
(1,024–2,566)
Pāpā 2010 0.81 ± 0.02
(0.13–2.09)		 268 ± 5
(41–687)
2016 – –
2021 – –

Pueo

There was a single Pueo detection. The native owl was detected in the Northwest Kahuku tract (Appendix), above 2,200 m elevation, in Māmane / Meadow Ricegrass Subalpine Semi-natural Woodland.

Red-Billed Leiothrix

There were 196 Red-billed Leiothrix detections. The species occurred at 26.9% of stations surveyed at an average 0.42 BPC. Its distribution was greatest in the ʻŌlaʻa tract (Appendix), primarily in ’Ōhi’a – ’Ōlapa / (Hāpuʻu spp.) Montane Wet Forest, Koa / Hāpuʻu spp. Montane Woodland, and ’Ōhi’a / Hāpuʻu spp. Montane Wet Forest, where it occurred at 49.5% of stations surveyed and averaged 0.84 BPC. Density was estimated at 1.44 ± 0.01 birds/ha in 2020, corresponding to an abundance of 3,521 ± 19 birds—a significant increase since 2010 (Table 14). There were also significant increases in the Honomalino and Pāpā tracts. In the Mauna Loa Strip tract, the species occurred at 46.2% of stations at an average of 0.74 BPC, across a range of vegetation classes including Koa / Non-native Grass, Pūkiawe – ’A’ali’i Montane Shrubland, and Māmane – (Pūkiawe – ’A’ali’i) Montane Woodland. The 2020 density in this tract was 0.83 ± 0.01 birds/ha, for an abundance of 2,655 ± 27 birds—a negligible decrease since 2010.

Table 14. Red-billed Leiothrix density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
East Rift Zone 2010 0.12 ± <0.01
(0–0.44)		 279 ± 10
(0–1,000)
2015 – –
2020 – –
Honomalino 2010 0.07 ± <0.01
(0–0.22)		 114 ± 3
(0–372)
2016 0.23 ± <0.01
(0.08–0.41)		 382 ± 4
(138–686)
2021 0.79 ± 0.01
(0.47–1.24)		 1,335 ± 10
(802–2,094)
Mauna Loa South Flank 2010 0.24 ± <0.01
(0.09–0.43)		 1,114 ± 12.17
(422–1,961)
2016 0.10 ± <0.01
(0–0.31)		 473 ± 12
(0–1,429)
2021 0.27 ± <0.01
(0.04–0.61)		 1,234 ± 21
(195–2,802)
Mauna Loa Strip 2010 0.90 ± 0.01
(0.30–2.05)		 2,870 ± 47
(962–6,510)
2015 0.54 ± 0.01
(0.25–0.96)		 1,708 ± 18
(797–3,051)
2020 0.83 ± 0.01
(0.47–1.46)		 2,655 ± 27
(1,485–4,648)
ʻŌlaʻa 2010 1.13 ± 0.01
(0.69–1.73)		 2,774 ± 21
(1,693–4,226)
2015 1.50 ± 0.01
(1.01–2.26)		 3,661 ± 24
(2,465–5,534)
2020 1.44 ± 0.01
(1.03–2.00)		 3,521 ± 19
(2,529–4,881)
Pāpā 2010 – –
2016 0.24 ± 0.01
(0–0.87)		 80 ± 3
(0–288)
2021 0.47 ± 0.02
(0–1.79)		 155 ± 5
(0–589)

Scaly-Breasted Munia

There were four detections on three stations of the Scaly-breasted Munia (Lonchura punctulata). Two detections occurred in Koa / ’Ōhi’a Montane Dry Woodland in the Mauna Loa South Flank tract (4.3% occurrence; 0.04 BPC) and two in Pūkiawe – ’A’ali’i Montane Shrubland in the Mauna Loa Strip tract (1.1% occurrence; 0.02 BPC; Appendix).

Spotted Dove

Spotted Dove (Spilopelia chinensis) was detected five times, occurring at 3.2% of stations (0.03 BPC) in Hāpuʻu spp. montane forest within the ʻŌlaʻa tract and at 2.2% of stations (0.02 BPC) in Koa Semi-natural Montane Woodland within the Mauna Loa Strip tract (Appendix)

Warbling White-Eye

There were 1,356 detections of the Warbling White-eye, making it the most widely distributed non-native species recorded, occurring at 73.1% of stations surveyed for an average of 2.95 BPC. The species was most widespread in all vegetation classes of the East Rift Zone (98.2% occurrence; 6.02 BPC), ʻŌlaʻa (100% occurrence; 4.87 BPC), Mauna Loa Strip (91.2% occurrence; 3.53 BPC), and Mauna Loa South Flank (100% occurrence; 2.91 BPC) tracts. Population density was highest in the East Rift Zone tract, with an estimated 30.56 ± 0.10 birds/ha, corresponding to an abundance of 54,424 ± 179 birds—a significant increase since 2010 (Table 15). Densities were also relatively high in the ʻŌlaʻa tract. In 2015, the estimate there reached 41.46 ± 0.11 birds/ha, the highest density recorded for any species across all survey years. However, by 2020 density had significantly decreased since 2010 and was 33% lower than the 2015 peak. Densities also decreased in the Honomalino, Mauna Loa South Flank, Mauna Loa Strip, and Pāpā tracts. Densities were lowest in the Northwest Kahuku tract, where there was a negligible change since 2010, but with a 2021 estimated abundance of just 236 ± 4 birds.

Table 15. Warbling White-eye density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
East Rift Zone 2010 23.20 ± 0.13
(16.83–32.74)		 52,303 ± 285
(37,931–73,798)
2015 26.68 ± 0.09
(21.86–32.58)		 47,524 ± 156
(38,935–58,024)
2020 30.56 ± 0.10
(25.00–37.41)		 54,424 ± 179
(44,529–66,622)
Honomalino 2010 6.29 ± 0.03
(4.60–8.52)		 10,617 ± 53
(7,773–14,385)
2016 4.56 ± 0.02
(3.50–5.90)		 7,696 ± 33
(5,905–9,952)
2021 4.37 ± 0.02
(3.16–5.92)		 7,371 ± 37
(5,334–9,998)
Mauna Loa South Flank 2010 15.34 ± 0.05
(12.41–19.34)		 70,436 ± 252
(57,015–88,814)
2016 11.97 ± 0.03
(10.18–14.37)		 54,989 ± 157
(46,771–66,018)
2021 13.07 ± 0.05
(10.09–17.09)		 60,052 ± 252
(46,341–78,479)
Mauna Loa Strip 2010 9.91 ± 0.04
(7.48–12.97)		 31,517 ± 143
(23,797–41,271)
2015 12.19 ± 0.06
(9.11–16.00)		 38,765 ± 178
(28,988–50,909)
2020 7.45 ± 0.03
(5.80–9.85)		 23,711 ± 100
(18,451–31,333)
Northwest Kahuku 2010 0.24 ± 0.01
(0–0.62)		 214 ± 5
(0–550)
2016 0.21 ± <0.01
(0.02–0.48)		 187 ± 3
(18–424)
2021 0.27 ± <0.01
(0.05–0.59)		 236 ± 4
(40–521)
ʻŌlaʻa 2010 36.72 ± 0.09
(31.97–42.80)		 89,812 ± 223
(78,193–104,697)
2015 41.46 ± 0.11
(35.36–49.59)		 101,419 ± 274
(86,498–121,289)
2020 27.88 ± 0.07
(24.17–32.61)		 68,192 ± 168
(59,116–79,775)
Pāpā 2010 0.56 ± 0.01
(0–1.47)		 183 ± 4
(0–485)
2016 2.75 ± 0.03
(1.33–4.76)		 903 ± 9
(439–1,566)
2021 – –

Wild Turkey

There were five detections of the Wild Turkey (Meleagris gallopavo). Each detection was in Kikuyu Grass Semi-natural Herbaceous Vegetation and Māmane / Meadow Ricegrass Subalpine Semi-natural Woodland within the Northwest Kahuku tract (4.2% occurrence; 0.07 BPC; Appendix).

Yellow-Billed Cardinal

There was a single detection of the Yellow-billed Cardinal (Paroaria capitata). The detection was in ’Ōhi’a / Hāpuʻu spp. Montane Wet Forest near the Nāulu trail in the East Rift Zone tract (Appendix).

Yellow-Fronted Canary

There were 83 detections of the Yellow-fronted Canary. The highest occurrence of 42.6% was in ʻŌhi’a / Kikuyu Grass Semi-natural Woodland within the Mauna Loa South Flank tract, where it averaged 0.72 BPC. The species was also detected within the East Rift Zone (14.5% occurrence; 0.20 BPC), Mauna Loa Strip (20.9% occurrence; 0.37 BPC), and Honomalino (5.1% occurrence; 0.05 BPC) tracts (Appendix). Detections were in a mix of vegetation classes, such as ’Ōhi’a / Kikuyu Grass Semi-natural Woodland, ʻŌhi’a / Uluhe Lowland Mesic Woodland, ʻŌhi’a / Hāpuʻu spp. (Cibotium spp.) Montane Wet Forest, and Pūkiawe – ’A’ali’i Montane Shrubland. This species irrupted within the survey area after 2010, when no individuals were detected. Density peaked in the Mauna Loa South Flank tract in 2015 at 3.43 ± 0.02 birds/ha, corresponding to an estimated abundance of 15,743 ± 73 birds. By 2021, however, density had decreased significantly, with an estimated abundance of 6,103 ± 54 birds in the tract (Table 16). Significant decreases over the same period were also observed in the Honomalino, Northwest Kahuku, and Pāpā tracts.

Table 16. Yellow-fronted Canary density (birds/ha) and estimated abundance (including SE and 95% CI) within each tract from the 2010, 2015–2016, and 2020–2021 surveys.
Tract Year Density ± SE
(95% CI)		 Total Abundance ± SE
(95% CI)
East Rift Zone 2010 – –
2015 0.06 ± <0.01
(0–0.22)		 102 ± 4
(0–394)
2020 0.37 ± <0.01
(0.14–0.69)		 661 ± 8
(245–1,222)
Honomalino 2010 – –
2016 0.62 ± 0.01
(0.26–1.09)		 1,039 ± 11
(435–1,837)
2021 0.09 ± <0.01
(0–0.21)		 144 ± 3
(0–358)
Mauna Loa South Flank 2010 – –
2016 3.43 ± 0.02
(2.61–4.56)		 15,743 ± 73
(11,972–20,962)
2021 1.33 ± 0.01
(0.73–2.15)		 6,103 ± 54
(3,331–9,869)
Mauna Loa Strip 2010 – –
2015 0.05 ± <0.01
(0–0.16)		 152 ± 5
(0–520)
2020 0.65 ± 0.01
(0.37–1.02)		 2,056 ± 17
(1,166–3,251)
Northwest Kahuku 2010 – –
2016 0.17 ± <0.01
(0.03–0.39)		 152 ± 3
(28–342)
2021 – –
ʻŌlaʻa 2010 – –
2015 0.02 ± <0.01
(0–0.07)		 50 ± 2
(0–179)
2020 – –
Pāpā 2010 – –
2015 1.80 ± 0.02
(0.81–3.47)		 591 ± 7
(266–1,140)
2021 – –

Zebra Dove

There were three Zebra Dove (Geopelia striata) detections on three stations, each of which were within the Kahuku Unit side of the Honomalino tract (3.8% occurrence; 0.04 BPC), in ’Ōhi’a Montane Woodland (Appendix).

2020–2021 Habitat Results

Habitat variables were measured at 445 landbird monitoring stations in 2020–2021. Canopy height and canopy cover were recorded at 444 of the stations (NPS Datastore - Habitat characteristics of landbird monitoring survey stations). The dominant canopy height was over 10 m at 43.0% of stations, from 6–10 m at 43.0% of stations, and 2–5 m at 14.0% of stations surveyed. A closed canopy cover classification was recorded at 33.6% of stations, and open canopy cover was recorded at 31.8% of stations. Shorter tree heights (2–5 m and 6–10 m) and scattered to very scattered canopy cover classifications were more prevalent in the Mauna Loa Strip, Northwest Kahuku, and Pāpā tracts. ʻŌhi’a was the dominant canopy species at 23.6% of the 444 stations surveyed and was the most common dominant canopy species in most of the tracts (NPS Datastore - Habitat characteristics of landbird monitoring survey stations). ʻŌlaʻa was the only tract in which ʻōhi’a did not occur as a dominant canopy class; the most common dominant canopy class in ʻŌlaʻa was tree ferns (Cibotium spp.), sub-dominant with ʻōhi’a, followed by a grouped class of native trees. Northwest Kahuku was the only other tract in which ʻōhi’a was not the most common dominant canopy species; the most common dominant canopy species in Northwest Kahuku was māmane. After ʻōhi’a, the most common dominant canopy class was co-dominant koa and ʻōhi’a at 8.3% of stations. The East Rift Zone was the only tract in which non-native trees were recorded in dominant canopy classes, with firetree (Morella faya) recorded as co-dominant, sub-dominant, or dominant with native species sub-dominant at six of 55 stations (10.9%), and the grouped class of introduced trees recorded as sub-dominant or dominant with native species sub-dominant at three stations. In the Mauna Loa Strip tract, the dominant canopy class was dead koa at 11 of 88 stations (12.5%); at four other stations, the dominant canopy classes were recorded as dead māmane, dead (unidentified species), burned koa, and co-dominant burned ʻaʻaliʻi and burned pūkiawe.

Dominant understory classes were recorded at all 445 stations (NPS Datastore - Habitat characteristics of landbird monitoring survey stations). The most common dominant understory classes in the East Rift Zone were native ferns and native shrubs, recorded at 23.6% of stations. In Honomalino, the most common dominant understory class was introduced grasses (35.5% of stations). Introduced grasses dominant with native ferns sub-dominant was recorded at 55.3% of stations in Mauna Loa South Flank. The most common dominant understory class in Mauna Loa Strip was bare ground, followed by native shrubs, which was recorded at 31.1% of stations. In Northwest Kahuku, the most common dominant understory class was bare ground, with introduced grasses, introduced shrubs, and native shrubs representing decreasing levels of sub-dominance at eight of 72 stations (11.1%). Native shrubs dominant with introduced shrubs sub-dominant was the most common understory class in ʻŌlaʻa, recorded at 26.6% of stations. In Pāpā, the most common dominant understory class was native grasses with native shrubs sub-dominant (36.4% of stations). Understory classes were highly variable across the entire survey area. The most common dominant understory class across all 445 stations was introduced grasses, recorded at 7.4% of stations. Introduced grasses, bare ground, native shrubs, native ferns, and introduced shrubs accounted for most of the dominant, co-dominant, and sub-dominant classifications within the survey area.

Discussion

Landbirds

The 2020–2021 HAVO landbird survey produced updated estimates of distribution and occurrence for 29 landbird species. Density and abundance were estimated for five native and seven non-native species, with results offering insights into population changes and the influence of ecological stressors, including habitat degradation, invasive species, disease, wildfires, and climate change. The seven survey tracts spanned a range of volcanic substrates, elevations, and forest types, providing perspective on how native and non-native birds are responding to environmental conditions. These findings can help prioritize conservation efforts and guide adaptive management strategies to support the long-term persistence of native landbirds in HAVO.

ʻApapane and Hawaiʻi ʻAmakihi remained the most abundant and widespread native species in the survey area. ʻApapane densities increased in Honomalino, Mauna Loa South Flank, and Pāpā, but declined in the remaining tracts, which indicates populations are influenced locally by stressors and habitat conditions. Similarly, Hawai’i ʻAmakihi populations showed significant increases in Mauna Loa South Flank and Mauna Loa Strip, likely benefiting from their partial resistance to avian malaria (Foster et al. 2007; Samuel et al. 2015; Woodworth et al. 2005). However, densities remained low in the East Rift Zone and ʻŌlaʻa tracts, where the combination of avian malaria, high rainfall, and less favorable habitat conditions limit population growth despite the species’ general resilience elsewhere (Judge et al. 2017). ʻŌlaʻa receives among the highest rainfall on the island, averaging more than 4,000 mm per year (Price et al. 2007), which may further constrain Hawaiʻi ʻAmakihi populations and explain why densities have been historically low there (Camp et al. 2009; Scott et al. 1986).

The federally threatened ʻIʻiwi was detected in the Honomalino tract with a slight increase in density; however, its absence from the Mauna Loa South Flank, Mauna Loa Strip, and other tracts demonstrates ongoing range contraction. These contractions are largely driven by the upward expansion of avian malaria, enabled by climate change–induced warming that allows cold-intolerant mosquitoes and the malaria parasite to persist at higher elevations (LaPointe et al. 2010; Paxton et al. 2013). Habitat degradation can also contribute to population declines, as invasive plants and ungulates reduce the availability of high-quality foraging and nesting sites (Atkinson et al. 2000; Gorresen et al. 2005; Paxton et al. 2013). Rapid ʻŌhiʻa Death (ROD), caused by the fungal pathogens Ceratocystis lukuohia and C. huliohia, presents an additional challenge to native forest bird habitat (Barnes et al. 2018). ROD has resulted in widespread ʻōhiʻa mortality, altering forest structure, microclimate, and nectar availability—resources that are critical for nectarivores such as ʻIʻiwi (Fortini et al. 2019; Perroy et al. 2021; Vaughn et al. 2023). In the upper windward areas of Kahuku and Kaʻū Forest Reserve, ROD has affected more than two ʻōhiʻa crowns per hectare (Vaughn et al. 2023), including areas where ʻIʻiwi abundance has declined since the early 1990s—even at cooler elevations above 1,500 m (Judge et al. 2024). These patterns are consistent with other regions of the island, such as Hakalau Forest National Wildlife Refuge, where ʻIʻiwi populations remained stable for decades. Since 2010, however, monitoring has documented declining densities of ʻIʻiwi within closed-canopy forests and an overall decline across the refuge (Kendall et al. 2023).

Although the Mauna Loa Strip tract lies mostly above the typical mosquito breeding range (Reiter and LaPointe 2009), birds may still be exposed to avian malaria through dispersing female mosquitoes capable of reaching higher elevations (LaPointe 2008). Nevertheless, the disappearance of ʻIʻiwi from this area cannot be attributed solely to disease. Persistently low densities of ʻŌmaʻo and declining numbers of Hawaiʻi ʻElepaio—species considered tolerant or resistant to avian malaria (Atkinson et al. 2001; VanderWerf et al. 2006)—point to the influence of additional ecological stressors. Decades of ungulate browsing severely degraded vegetation prior to successful feral goat and pig removal in the 1970s and 1980s (Katahira et al. 1993), and recovery of key native plant species has been slow due to sparse seed sources and limited recruitment. HAVO has since reforested areas of Mauna Loa Strip, planting nearly 10,000 seedlings of māmane, hōʻawa (Pittosporum hosmeri and P. terminalioides), ʻiliahi (Santalum paniculatum), and naio (S. McDaniel, NPS, oral communication, March 2022). However, the 2018 Keauhou Ranch Brush Fire burned approximately 1,200 ha of native habitat (NPS 2018), further compounding habitat degradation. The area has a history of wildfire (Belfield and Pratt 2002; Loh et al. 2007) and ʻōhiʻa dieback—a successional process that has impacted forest canopies of Mauna Loa Strip and other park regions (Hodges et al. 1986; Mueller-Dombois et al. 1977). These disturbances have contributed to the invasion of weedy grasses and reduced native plant diversity (Belfield and Pratt 2002). The cumulative effects of these pressures on a landscape already characterized by extensive lava flows, sparse vegetation, and fragmented montane shrublands (Green et al. 2015) are compounded by the degraded pastureland portions of Kapāpala and Keauhou Ranch that border the tract. These combined factors have contributed to habitat fragmentation and isolation, which may render parts of Mauna Loa Strip a population sink despite ongoing restoration efforts.

ʻŌmaʻo abundance showed mixed differences compared to previous surveys. The most notable decrease occurred in the East Rift Zone, which in 2010 had the highest ʻŌmaʻo densities in the entire survey area. The 2010 survey occurred shortly after the area was cleared of feral pigs (Judge et al. 2011), but by 2020, fencing disrepair caused by reduced access due to volcanic eruption activity allowed pigs to re-establish and cause extensive understory damage, likely contributing to declines in ʻŌmaʻo and other species. In contrast, ʻŌmaʻo showed increased densities in the Mauna Loa South Flank and ʻŌlaʻa tracts, where the surveyed portions of the tracts have been ungulate-free (Judge et al. 2017; Loh and Tunison 1999), aside from occasional ingression events. As a principal native seed disperser, stable to increasing populations of ʻŌmaʻo contribute to forest regeneration and native plant recruitment (Pejchar et al. 2018), which in turn supports higher densities of native birds. ʻŌmaʻo were not detected in the three leeward Mauna Loa tracts—Honomalino, Northwest Kahuku, and Pāpā—during the 2016 or 2021 surveys. In 2010, there were 14 detections in Northwest Kahuku and nine detections in Pāpā. Prior to those detections, ʻŌmaʻo had been considered extirpated from leeward areas of the island since 1978 (Scott et al. 1986; van Riper and Scott 1979). However, incidental observations by TNC personnel and evidence of populations occupying native scrub subalpine and alpine habitats (Judge et al. 2012) suggest that ʻŌmaʻo may persist in leeward areas of Mauna Loa.

Hawaiʻi ʻElepaio showed mixed patterns across the HAVO survey area. Increases in density occurred in the leeward tracts of Honomalino and Pāpā and the mid-elevation windward tract of ʻŌlaʻa—areas where declines were documented in the late 20th century (Gorresen et al. 2005). Predation, particularly by black rats, has been identified as a primary factor influencing Hawaiʻi ʻElepaio and Oʻahu ʻElepaio (C. ibidis) populations (Sarr et al. 1998; VanderWerf 2001, 2009; VanderWerf et al. 2011). In study areas within and adjacent to the Mauna Loa Strip tract, Banko et al. (2019) reported that 24% of Hawaiʻi ʻElepaio nests failed due to rat predation, and that targeted rodent control increased nesting success for Hawaiʻi ʻElepaio and other passerines. Habitat degradation from ungulate browsing has been another significant stressor, especially in areas where native understory is critical for foraging and nesting. For instance, low densities of Hawaiʻi ʻElepaio in the Northwest Kahuku tract—where we estimated only 27 ± 1 birds in 2021 (an 88% decline since 2010)—was likely associated with poor habitat conditions caused by sheep grazing. In contrast, population growth in Honomalino and neighboring Pāpā may be associated with conservation interventions. Efforts such as ungulate exclusion and removal, along with localized predator control in these tracts (TNC Hawaiʻi 2021, 2023), may have led to improved habitat quality and enhanced reproductive success, thereby contributing to observed increases in Hawaiʻi ʻElepaio abundance.

Non-native bird species continue to co-dominate avian communities in most areas of HAVO, with species such as the Warbling White-eye, Red-billed Leiothrix, and Northern Cardinal outnumbering native species in many tracts. The rapid expansion of species like the Japanese Bush Warbler highlights the capacity of non-native birds to establish and proliferate in ʻōhiʻa-dominated forests. Beyond their numerical dominance, non-native birds can influence native populations through multiple ecological mechanisms. As carriers of avian malaria and other pathogens, they serve as reservoirs that facilitate disease transmission to susceptible native species (McClure et al. 2020). They also modify habitats and resource availability: generalists such as Red-billed Leiothrix and Warbling White-eye disperse invasive plants (Chimera and Drake 2010; Vizentin-Bugoni et al. 2019), compete with native passerines for food resources due to dietary overlap (Banko et al. 2015; Mountainspring and Scott 1985), and displace native birds from foraging and nesting sites through aggressive interactions (Foster and Robinson 2007). Collectively, these mechanisms may reduce reproductive success and survival of native species.

Observed changes in bird densities at HAVO illustrate potential dynamics between native and non-native species. This is most notably illustrated between ʻApapane and Warbling White-eye where, in four of seven tracts, their densities were negatively correlated, with the most pronounced shift in the East Rift Zone tract where ʻApapane densities decreased by nearly 12 birds/ha since 2010, while Warbling White-eye densities increased to more than seven birds/ha over the same period. This negative association is indicative of interspecific competition, as the Warbling White-eye is a generalist forager whose diet overlaps with ʻApapane and other native nectarivores (Burnett and Downs 2020). However, it is difficult to directly attribute these changes to competition alone, since multiple ecological and environmental factors may also contribute. Similar patterns consistent with competition have been documented across the main Hawaiian Islands (Mountainspring and Scott 1985; Ralph 1991), and in HAVO, recent estimates show that ʻIʻiwi and Hawaiʻi ʻElepaio occurred at only a fraction of Warbling White-eye densities or were absent altogether.

The endangered ʻAkiapōlāʻau, Hawaiʻi ʻĀkepa, and ʻAlawī were not detected in any of the tracts surveyed. ʻAlawī were previously detected in Honomalino (three individuals) and Pāpā (one individual) in 2010, and again in Honomalino (one individual) in 2016. It remains unclear whether small, remnant populations of ʻAlawī persist in these tracts or whether the species has been extirpated from the area. More frequent surveys and alternative monitoring techniques, such as bioacoustic sampling, would help distinguish between true absence and low detectability due to seasonal variation or population decline (Hutschenreiter et al. 2024; Navine et al. 2024). Outside of the 2020‒2021 survey area, HAVO harbors endangered species within montane woodlands of windward Kahuku, where surveys in 2019 indicated stable to increasing trends of Hawaiʻi ʻĀkepa and ʻAlawī (Judge et al. 2024). The core range of each species, along with ʻAkiapōlāʻau, are concentrated in mesic closed-canopy ʻōhiʻa-koa forests of the state-managed Kaʻū Forest Reserve. Because these habitats, like those in Honomalino, extend across both state and park lands, effective conservation of Hawaiian forest birds can be supported by sustained cross-boundary management.

Restoring and protecting native forest habitats, particularly in cooler, high-elevation areas, represents a viable path for safeguarding native bird populations. Continued exclusion of ungulates, active reforestation, and management of wildfire-prone landscapes can help to maintain and improve habitat quality. At the same time, suppressing mosquito populations through strategies such as the Incompatible Insect Technique (Beebe et al. 2021; Zheng et al. 2019) and larvicides like Bacillus thuringiensis israelensis (Després et al. 2011; Lacey 2007) can slow the advance of avian malaria into upper elevation refugia. These actions, when integrated with targeted predator control and containment of ROD, may help stabilize declining populations and prevent extirpation. Continued collaboration among park managers, neighboring landowners, and conservation partners, with adaptive strategies informed by rigorous monitoring and ecological research, can support conservation efforts.

A primary limitation of this study was the inability to fit regression-based models (e.g., generalized linear or mixed-effects models) to evaluate long-term trends in bird populations. This constraint arose from the small number of temporally distinct surveys (2010, 2015–2016, 2020–2021), which provides insufficient degrees of freedom for trend estimation. In the absence of a model for change over continuous time, we relied on pairwise comparisons using two-sample z-tests within an equivalence-testing framework. Although such tests can identify differences between survey periods, they do not accommodate temporal autocorrelation, interannual variability, or time-varying sampling error—factors that are critical for inference on population trajectories and stability (Thomas and Martin 1996). Regression frameworks could also allow inclusion of covariates (e.g., climate, disease prevalence, elevation, vegetation) to evaluate putative drivers and mechanisms of decline or persistence (Fewster et al. 2000). Methodological evaluations suggest that reliable estimation of linear time trends generally requires a minimum of five temporally independent surveys, with 8–10 survey years recommended to achieve adequate power in the presence of moderate variability and autocorrelation (Bart et al. 2003; Sauer and Link 2002; Thomas 1996; Thompson et al. 1998). The cumulative effects of disease transmission, habitat alteration, and interspecific interactions further complicate detection and interpretation of trends when temporal resolution is limited.

Interpreting population variability in HAVO requires consideration of compounding threats, particularly the ongoing expansion of avian malaria into high-elevation forests as the Southern house mosquito tracks rising temperature regimes (Atkinson et al. 2014; Samuel et al. 2011). The observed decline in ʻIʻiwi and absence of other historically present species such as Hawaiʻi ʻĀkepa are consistent with patterns expected under increasing disease pressure, rather than solely with natural demographic fluctuations. These trends highlight how an integrated management response that combines habitat protection and restoration, sustained predator control, and accelerated planning can be used to improve nesting success and for landscape-scale mosquito suppression. Vector control strategies—including the Incompatible Insect Technique, deployment of biological larvicides (e.g., Bacillus thuringiensis israelensis), and complementary approaches currently under development—are experimental and carry significant logistical and financial costs, yet represent the only current feasible means of reducing transmission in situ. The park’s avifauna faces an increasing risk of following the trajectory of populations on Kauaʻi and Maui, where disease-driven collapses have already occurred (Hunt et al. 2025; Judge et al. 2021), which could be addressed with early integration of tools into HAVO’s adaptive management framework.

Habitats

We used habitat information collected during surveys to identify influencing covariates in modeling detection functions for estimating bird densities, but the 2020–2021 habitat data did not substantially improve abundance estimates. Habitat surveys are nevertheless an important component of landbird monitoring efforts because the information can be used to better understand the dynamics of bird populations and habitat quality. Habitat conditions such as canopy cover and density influence food availability, which in turn may affect bird population densities in the area (Fretz 2002). If changes in bird populations are detected, having long-term habitat information may enable identification of the causative factors driving those changes. Furthermore, the information gathered from the habitat surveys serves as an overview and provides general descriptions of habitat conditions at our study plots. With continuous monitoring, habitat surveys offer insights for effective future management, such as control of ungulates, mosquitoes, mammalian predators, and invasive plants. Canopy and understory vegetation information may help to locate and monitor the spread of invasive plants, which have already become an acute problem in Hawaiʻi for the preservation of native ecosystems and bird habitats (Loope et al. 2001). Lastly, the habitat information can also be incorporated into other vital signs monitoring programs. Canopy information may complement satellite imagery to improve knowledge of the vegetation composition in an area. Understory vegetation information may reveal habitat structures that cannot be surveyed using remote sensing methods.

Our habitat surveys encompass a broad range of areas within HAVO and can detect invasive plants—such as banana passionfruit (Passiflora tripartita var. mollissima), night-blooming jasmine (Cestrum nocturnum), Koster’s curse (Miconia crenata), and others—at incipient stages before major infestations occur. In 2020–2021, firetree and a mixed class of introduced trees were recorded as dominant canopy types at 16.4% of East Rift Zone stations, representing just 0.02% of all HAVO stations. Surveyors observed alien Rubus spp. in Mauna Loa South Flank and Mauna Loa Strip; kāhili ginger, strawberry guava (Psidium cattleyanum), and palmgrass (Setaria palmifolia) in ʻŌlaʻa; and fireweed (Senecio madagascariensis) in Honomalino and Northwest Kahuku. In ʻŌlaʻa, surveyors also noted dead ʻōhiʻa, while browning leaves were observed in Northwest Kahuku—potential indicators of ROD, a disease that contributes to habitat loss and negatively affects native birds (Camp et al. 2019). The disease has been recorded in other areas of HAVO and is expected to continue spreading (Vaughn et al. 2023); however, state and federal land managers have implemented protocols and outreach campaigns to reduce its spread and impact (Cannon et al. 2022). Surveyors additionally recorded the presence of feral sheep and/or European mouflon in Honomalino and Northwest Kahuku, feral pigs in the East Rift Zone and ʻŌlaʻa, and high densities of mosquitoes in ʻŌlaʻa. Ongoing habitat surveys can provide additional updates on the condition of landbird habitats and emerging threats to the ecosystem.

Literature Cited

  • Athens, J.S., T.M. Rieth, and T.S. Dye. 2014. A paleoenvironmental and archaeological model-based age estimate for the colonization of Hawaiʻi. American Antiquity 79(1): 144–155.

  • Atkinson, C.T., J.K. Lease, B.M. Drake, and N.P. Shema. 2001. Pathogenicity, serological responses and diagnosis of experimental and natural malarial infections in native Hawaiian thrushes. Condor 103: 209–218.

  • Atkinson, C.T., R.B. Utzurrum, D.A. LaPointe, R.J. Camp, L.H. Crampton, J.T. Foster, and T.W. Giambelluca. 2014. Changing climate and the altitudinal range of avian malaria in the Hawaiian Islands–an ongoing conservation crisis on the island of Kauaʻi. Global Change Biology 20(8): 2426–2436.

  • Atkinson, C.T., R.J. Dusek, K.L. Woods, and W.M. Iko. 2000. Pathogenicity of avian malaria in experimentally infected Hawaiʻi ʻAmakihi. Journal of Wildlife Disease 37: 20–27.

  • Atkinson, I.A.E. 1977. A reassessment of factors, particularly Rattus rattus L., that influenced the decline of endemic forest birds in the Hawaiian Islands. Pacific Science 31(2): 109–133.

  • Banko, P.C. 1992. Constraints on productivity of wild Nēnē or Hawaiian Geese Branta sandvicensis. Wildfowl 43(43): 99–106.

  • Banko, P.C., K.A. Jaenecke, R.W. Peck, and K.W. Brinck. 2019. Increased nesting success of Hawaiʻi ʻElepaio in response to the removal of invasive black rats. The Condor 121(2): 1–12.

  • Banko, P.C., R.W. Peck, K.W. Brinck, and D.L. Leonard. 2015. Richness, diversity, and similarity of arthropod prey consumed by a community of Hawaiian forest birds. Hawaiʻi Cooperative Studies Unit Technical Report HCSU-066, University of Hawaiʻi at Hilo, Hilo, Hawaiʻi.

  • Banko, W.E., and P.C. Banko. 2009. Historic decline and extinction. Pages 25–58 in T.K. Pratt, C.T. Atkinson, P.C. Banko, J.D. Jacobi, and B.L. Woodworth, editors. Conservation Biology of Hawaiian Forest Birds: Implications for Island Avifauna. Yale University Press, New Haven, Connecticut.

  • Barnes, I., A. Fourie, M.J. Wingfield, T.C. Harrington, D.L. McNew, L.S. Sugiyama, B.C. Luiz, W.P. Heller, and L.M. Keith. 2018. New Ceratocystis species associated with rapid death of Metrosideros polymorpha in Hawaiʻi. Persoonia-Molecular Phylogeny and Evolution of Fungi 40(1): 154–181.

  • Bart, J., B.D. Collins, and R.I.G. Morrison. 2003. Estimating population trends with a linear model. The Condor 105(2): 367–372.

  • Beebe, N.W., D. Pagendam, B.J. Trewin, A. Boomer, M. Bradford, A. Ford, C. Liddington, A. Bondarenco, P.J. De Barro, J. Gilchrist, and C. Paton. 2021. Releasing incompatible males drives strong suppression across populations of wild and Wolbachia-carrying Aedes aegypti in Australia. Proceedings of the National Academy of Sciences 118(41): p.e2106828118.

  • Belfield, T.R., and L.W. Pratt. 2002. Rare plants of the Mauna Loa Special Ecological Area, Hawaiʻi Volcanoes National Park. Technical Report 130, USGS Pacific Island Ecosystems Research Center, Kilauea Field Station, Hawaiʻi.

  • Best, L.B. 1981. Seasonal changes in detection of individual bird species. Studies in Avian Biology 6: 252–261.

  • Buckland, S.T., E.A. Rexstad, T.A. Marques, and C.S. Oedekoven. 2015. Distance Sampling: Methods and Applications. Springer, London, United Kingdom.

  • Burnett, M.J. and C.T. Downs. 2020. Warbling White-eye (Zosterops japonicus Temminck & Schlegel 1845). Pages 170–174 in C.T. Downs and L.A. Hart, editors. Invasive birds: global trends and impacts. CABI Books, Wallingford, United Kingdom.

  • Camp, R.J., D.A. LaPointe, P.J. Hart, D.E. Sedgwick, and L.K. Canale. 2019. Large-scale tree mortality from Rapid ʻŌhiʻa Death negatively influences avifauna in lower Puna, Hawaiʻi Island, USA. The Condor 121(2): duz007.

  • Camp, R.J., P.M. Gorresen, T.K. Pratt, and B.L. Woodworth. 2009. Population trends of native Hawaiian forest birds, 1976–2008: the data and statistical analyses. Hawaiʻi Cooperative Studies Unit Technical Report HCSU-012. University of Hawaiʻi at Hilo, Hilo, Hawaiʻi.

  • Camp, R.J., T.K. Pratt, C. Bailey, and D. Hu. 2011. Landbirds vital sign monitoring protocol – Pacific Island Network. Natural Resources Report NPS/PACN/NRR—2011/402. National Park Service, Fort Collins, Colorado.

  • Camp, R.J., N. Seavey, M.H. Reynolds, and P.M. Gorresen. 2008. A statistical test to show negligible trend: comment. Ecology 89(5): 1469–1472.

  • Cannon, P., J.B. Friday, T. Harrington, L. Keith, M. Hughes, R. Hauff, F. Hughes, R. Perroy, D. Benitez, et al. 2022. Rapid ’Ōhi’a Death in Hawai’i. Pages 267–289 in F. O. Asiegbu and A. Kovalchuk, editors. Forest Microbiology, Volume 2: Forest Tree Health. Academic Press, San Diego, California.

  • Chesser, R.T., S.M. Billerman, K.J. Burns, C. Cicero, J.L. Dunn, B.E. Hernández-Baños, R.A. Jiménez, Oscar Johnson, N.A. Mason, and P.C. Rasmussen. 2025. Check-list of North American Birds (online). American Ornithological Society. https://checklist.americanornithology.org/taxa/

  • Chimera, C.G., and D.R. Drake. 2010. Patterns of seed dispersal and dispersal failure in a Hawaiian dry forest having only introduced birds. Biotropica 42(4): 493–502.

  • Després, L., C. Lagneau, and R. Frutos. 2011. Using the bio-insecticide Bacillus thuringiensis israelensis in mosquito control. Pesticides in the Modern World – Pests Control and Pesticides Exposure and Toxicity Assessment 10: 93–126.

  • Doremus, H., and J.E. Pagel. 2001. Why delisting may be forever: perspectives on delisting under the U.S. Endangered Species Act. Conservation Biology 15: 1258–1263.

  • Fewster, R.M., S.T. Buckland, G.M. Siriwardena, D.E. Baillie, and J.D. Wilson. 2000. Analysis of population trends for farmland birds using generalized additive models. Ecology 81(7): 1970–1984.

  • Fortini, L.B., L.R. Kaiser, L.M. Keith, J. Price, R.F. Hughes, J.D. Jacobi, and J.B. Friday. 2019. The evolving threat of Rapid ’Ōhi ’a Death (ROD) to Hawai ’i’s native ecosystems and rare plant species. Forest Ecology and Management 448: 376–385.

  • Foster, J.T. and S.K., Robinson. 2007. Introduced birds and the fate of Hawaiian rainforests. Conservation Biology 21(5): 1248–1257.

  • Foster, J.T., B.L. Woodworth, L.E. Eggert, P.J. Hart, D. Palmer, D.C. Duffy, and R.C. Fleischer. 2007. Genetic structure and evolved malaria resistance in Hawaiian honeycreepers. Molecular Ecology 16(22): 4738–4746.

  • Fretz, J.S. 2002. Scales of food availability for an endangered insectivore, the Hawaiʻi ʻĀkepa. The Auk 119(1): 166–174.

  • Gill, F., D. Donsker, and P. Rasmussen, editors. 2026. IOC World Bird List – Version 15.2.

  • Gorresen, P.M., R.J. Camp, T.K. Pratt, and B.L. Woodworth. 2005. Status of forest birds in the central windward region of Hawaiʻi Island: population trends and power analyses. U.S. Geological Survey, Biological Resources Discipline, Open-File Report 2005 1441. U.S. Department of the Interior, Washington, D. C.

  • Green, K., M. Hall, C. Lopez, A. Ainsworth, M. Selvig, K. Akamine, S. Fugate, K. Schulz, D. Benitez, et al. 2015. Vegetation mapping inventory project: Hawai’i Volcanoes National Park. Natural Resource Report NPS/PACN/NRR—2015/966, National Park Service, Fort Collins, Colorado.

  • Grossman, D.H., D. Faber-Langendoen, A.S. Weakley, M. Anderson, P.S. Bourgeron, R. Crawford, K. Goodin, S. Landaal, K. Metzler, et al. 1998. International classification of ecological communities: terrestrial vegetation of the United States. Volume I. The national vegetation classification system: development, status, and applications. The Nature Conservancy, Arlington, Virginia.

  • Hodges, C.S., K.T. Adee, J.D. Stein, H.B. Wood, and R.D. Doty. 1986. Decline of ohia (Metrosideros polymorpha) in Hawaiʻi: a review. USDA Forest Service, General Technical Report. PSW-86. Pacific Southwest Research Station, Berkeley, California.

  • Hunt, N.J., L.H. Crampton, T.A. Winter, J.D. Alexander, R. Gilb, and R.J. Camp. 2025. Disease-driven collapse of the native Kauaʻi avifauna and the rise of introduced bird species. Biodiversity and Conservation 34: 3511–3533.

  • Hutschenreiter, A., E. Andresen, M. Briseño‐Jaramillo, A. Torres‐Araneda, E. Pinel‐Ramos, J. Baier, and F. Aureli. 2024. How to count bird calls? Vocal activity indices may provide different insights into bird abundance and behaviour depending on species traits. Methods in Ecology and Evolution 15(6): 1071–1083.

  • Jacobi, J.D. 1989. Vegetation maps of the upland plant communities of the islands of Hawaiʻi, Maui, Molokai, and Lanai. Technical Report 68. Cooperative National Park Resources Studies Unit, Department of Botany. University of Hawaiʻi, Honolulu, Hawaiʻi.

  • Judge, S.W., C.C. Warren, R.J. Camp, L.K. Berthold, H.L. Mounce, P.J. Hart, and R.J. Monello. 2021. Population estimates and trends of three Maui Island‐endemic Hawaiian Honeycreepers. Journal of Field Ornithology 92(2): 115–126.

  • Judge, S.W., J.M. Gaudioso, B. Hsu, R.J. Camp, and P.J. Hart. 2011. Pacific Island landbird monitoring annual report, Hawai’i Volcanoes National Park, tract group 1 and 2, 2010. Natural Resource Technical Report NPS/PACN/NRTR—2011/486. National Park Service, Fort Collins, Colorado.

  • Judge, S.W., J.M. Gaudioso, P.M. Gorresen, and R.J. Camp. 2012. Reoccurrence of ’Ōma ’o in leeward woodland habitat and their distribution in alpine habitat on Hawai ’i Island. The Wilson Journal of Ornithology 124(4): 675–681.

  • Judge, S.W., K.W. Brinck, A.S. Genz, L. Berry, J.M. Gaudioso, A.X. Wang, and R.J. Camp. 2024. Divergent trends in distribution and abundance of landbirds in low and high elevation habitats of the Kaʻū Rainforest. Science Report NPS/SR—2024/141. National Park Service, Fort Collins, Colorado.

  • Judge, S.W., R.J. Camp, D.E. Sedgwick, C.L. Squibb, and P.J. Hart. 2017. Pacific Island landbird monitoring report, Hawaiʻi Volcanoes National Park, 2015−2016: Tract Groups 1 and 2. Natural Resource Report NPS/PACN/NRR—2017/1407. National Park Service, Fort Collins, Colorado.

  • Katahira, L.K., P. Finnegan, and C.P. Stone. 1993. Eradicating feral pigs in montane mesic habitat at Hawaiʻi Volcanoes National Park. Wildlife Society Bulletin 21(3): 269–274.

  • Kendall, S.J., R.A. Rounds, R.J. Camp, A.S. Genz, T. Cady, and D.L. Ball. 2023. Forest bird populations at the Big Island National Wildlife Refuge Complex, Hawai’i. Journal of Fish and Wildlife Management 14(2): 410–432. https://doi.org/10.3996/JFWM-22-035

  • Kirch, P.V. 2011. When did the Polynesians settle Hawai’i? A review of 150 years of scholarly inquiry and a tentative answer. Hawaiian Archaeology 12: 3–26.

  • Lacey, L.A. 2007. Bacillus thuringiensis serovariety israelensis and Bacillus sphaericus for mosquito control. Journal of the American Mosquito Control Association 23(sp2): 133–163.

  • LaPointe, D.A. 2008. Dispersal of Culex quinquefasciatus (Diptera: Culicidae) in a Hawaiian rain forest. Journal of Medical Entomology 45(4): 600–609.

  • LaPointe, D.A., M.L. Goff, and C.T. Atkinson. 2010. Thermal constraints to the sporagonic development and altitudinal distribution of avian malaria Plasmodium relictum in Hawaiʻi. Journal of Parasitology 96(2): 318–324.

  • Loh, R., S. McDaniel, D. Benitez, M. Schultz, D. Palumbo, A. Ainsworth, K. Smith, T. Tunison, and M. Vaidya. 2007. Rehabilitation of seasonally dry ohia woodlands and mesic koa forest following the Broomsedge Fire, Hawaiʻi Volcanoes National Park. Technical Report No. 147. Pacific Cooperative Studies Unit, University of Hawaiʻi at Manoa, Honolulu, Hawaiʻi.

  • Loh, R.K., and J.T. Tunison. 1999. Vegetation recovery following pig removal in ʻŌlaʻa-Koa Rainforest Unit, Hawaiʻi Volcanoes National Park. Technical Report No. 123. Pacific Cooperative Studies Unit, University of Hawaiʻi at Manoa, Honolulu, Hawaiʻi.

  • Loope, L.L., F.G. Howarth, F. Kraus, and T.K. Pratt. 2001. Newly emergent and future threats of alien species to Pacific landbirds and ecosystems. Studies in Avian Biology 22: 291–294.

  • McClure, K.M., R.C. Fleischer, and A.M. Kilpatrick. 2020. The role of native and introduced birds in transmission of avian malaria in Hawaiʻi. Ecology 101(7): p.e03038.

  • Miller, D.L., E. Rexstad, L. Thomas, L. Marshall, and J.L. Laake. 2019. Distance sampling in R. Journal of Statistical Software 89(1): 1–28. https://doi.org/10.18637/jss.v089.i01

  • Mountainspring, S., and J.M. Scott. 1985. Interspecific competition among Hawaiian forest birds. Ecological Monographs 55(2): 219–239.

  • Mueller-Dombois, D., J.D. Jacobi, R.G. Cooray, and N. Balakrishnan. 1977. ʻOhiʻa rain forest study: final report. Cooperative National Park Resources Studies Unit Technical Report No. 20. Department of Botany, University of Hawaiʻi, Honolulu, Hawaiʻi.

  • National Park Service (NPS). 2018. Keauhou Ranch Brush Fire. Emergency Stabilization and Rehabilitation Plan for Hawai’i Volcanoes National Park. Internal document.

  • Navine, A.K., T. Denton, M.J. Weldy, and P.J. Hart. 2024. All thresholds barred: direct estimation of call density in bioacoustic data. Frontiers in Bird Science 3: p.1380636.

  • Olson, S.L., and H.F. James. 1982. Fossil birds from the Hawaiian Islands: evidence for wholesale extinction by man before Western contact. Science 217(4560): 633–635.

  • Olson, S.L., and H.F. James. 1984. The role of Polynesians in the extinction of the avifauna of the Hawaiian Islands. Pages 768–780 in P.S. Martin and R.G. Klein, editors. Quaternary Extinctions: A Prehistoric Revolution. University of Arizona Press, Tucson, Arizona.

  • Olson, S.L., and H.F. James. 1991. Descriptions of thirty-two new species of birds from the Hawaiian Islands: Part I. Non-Passeriformes. Ornithological Monographs (45): 1–88.

  • Paxton, E.H., P.M. Gorresen, and R.J. Camp. 2013. Abundance, distribution, and population trends of the iconic Hawaiian honeycreeper, the ’I’iwi (Vestiaria coccinea) throughout the Hawaiian Islands. U.S. Geological Survey Open-File Report 2013-1150, Reston, Virginia.

  • Pejchar, L., T. Gallo, M.B. Hooten, and G.C. Daily. 2018. Predicting effects of large‐scale reforestation on native and exotic birds. Diversity and Distributions 24(6): 811–819.

  • Perroy, R.L., T. Sullivan, D. Benitez, R.F. Hughes, L.M. Keith, E. Brill, K. Kissinger, and D. Duda. 2021. Spatial patterns of ’ōhi ’a mortality associated with rapid ’ōhi ’a death and ungulate presence. Forests 12(8): 1035.

  • Price, J., S.M. Gon III, J.D. Jacobi, and D. Matsuwaki. 2007. Mapping plant species ranges in the Hawaiian Islands: Developing a methodology and associated GIS layers. Hawaiʻi Cooperative Studies Unit Technical Report HCSU-008. University of Hawaiʻi at Hilo, Hilo, Hawaiʻi.

  • R Core Team. 2024. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/ (accessed on 08 May 2024).

  • Ralph, C.J., 1991. Population dynamics of land bird populations on Oahu, Hawaiʻi: fifty years of introductions and competition. Acta XX Congressus Internationalis Ornithologici, Christchurch, New Zealand 2-9 December 1990. 3: 1444–1457.

  • Reiter, M.E., and D.A. LaPointe. 2009. Larval habitat for the avian malaria vector Culex quinquefasciatus in alterated mid‑elevation mesic‑dry forests in Hawai’i. Journal of Vector Ecology 34(2): 208–216.

  • Samuel, M.D., P.H.F. Hobbelen, F. DeCastro, J.A. Ahumada, D.A. LaPointe, C.T. Atkinson, B.L. Woodworth, P.J. Hart, and D.C. Duffy. 2011. The dynamics, transmission, and population impacts of avian malaria in native Hawaiian birds: a modeling approach. Ecological Applications 21(8): 2960–2973.

  • Samuel, M.D., B.L. Woodworth, C.T. Atkinson, P.J. Hart, and D.A. LaPointe. 2015. Avian malaria in Hawaiian forest birds: infection and population impacts across species and elevations. Ecosphere 6:104. https://doi.org/10.1890/ES14-00393.1

  • Sarr, Z., N.P. Shema, and C.P. Stone. 1998. Nesting success and population status of the ʻElepaio (Chasiempis sandwichensis) in the Mauna Loa strip section of Hawaiʻi Volcanoes National Park. Cooperative National Park Resources Studies Unit Technical Report #118, University of Hawaiʻi at Manoa, Honolulu, Hawaiʻi.

  • Sauer, J.R., and W.A. Link. 2002. Hierarchical modeling of population stability and species group attributes from survey data. Ecology 83(6): 1743–1751.

  • Scott, J.M., and C.B. Kepler. 1985. Distribution and abundance of Hawaiian native birds: a status report. Pages 43–70 in S.A. Temple, editor. Bird Conservation 2. University of Wisconsin Press, Madison, Wisconsin.

  • Scott, J.M., S. Mountainspring, F.L. Ramsey, and C.B. Kepler. 1986. Forest bird communities of the Hawaiian Islands: their dynamics, ecology and conservation. Studies in Avian Biology No. 9.

  • Simon, J.C., T.K. Pratt, K.E. Berlin, J.R. Kowalsky, S.G. Fancy, and J.S. Hatfield. 2002. Temporal variation in bird counts within a Hawaiian rainforest. The Condor 104: 469–481.

  • Tear, T.H., J.M. Scott, P.H. Hayward, and B. Griffith. 1995. Recovery plans and the Endangered Species Act: are criticisms supported by data? Conservation Biology 9: 182–195.

  • The Nature Conservancy of Hawaiʻi (TNC Hawaiʻi). 2021. Final report: The Nature Conservancy’s Rare Species Enhancement Project. Unpublished data.

  • The Nature Conservancy of Hawaiʻi (TNC Hawaiʻi). 2023. Kona Hema Preserve Progress Report. Unpublished data.

  • Thomas, L. 1996. Monitoring long-term population change: Why are there so many analysis methods? Ecology 77: 49–58.

  • Thomas, L., and K. Martin. 1996. The importance of analysis method for breeding bird survey population trend estimates. Conservation Biology 10: 479–490.

  • Thomas, L., S.T. Buckland, E.A. Rexstad, J.L. Laake, S. Strindberg, S.L. Hadley, J.R.B. Bishop, T.A. Marques, and K.P. Burnham. 2010. Distance software: design and analysis of distance sampling surveys for estimating population size. Journal of Applied Ecology 47: 5–14.

  • Thompson, W.L., G.C. White, and C. Gowan. 1998. Monitoring vertebrate populations. Academic Press, San Diego, California.

  • Tweed, E., P.M. Gorresen, R.J. Camp, P.J. Hart, and T.K. Pratt. 2007. Forest bird inventory of the Kahuku unit of Hawaiʻi Volcanoes National Park. The Pacific Cooperative Studies Unit Technical Report #143, University of Hawaiʻi at Hilo, Hilo, Hawaiʻi.

  • U.S. Fish and Wildlife Service (USFWS). 2006. Revised recovery plan for Hawaiian forest birds. USFWS, Region 1, Portland, OR.

  • U.S. Fish and Wildlife Service (USFWS). 2019. Endangered and threatened wildlife and plants; reclassifying the Hawaiian Goose from endangered to threatened with a section 4(d) rule. Federal Register 84(69918): 69918–69947.

  • U.S. Fish and Wildlife Service (USFWS). 2020. Endangered and threatened wildlife and plants; removing the Hawaiian Hawk from the federal list of endangered and threatened wildlife. Federal Register 85(164): 164–189.

  • U.S. Fish and Wildlife Service (USFWS). 2023. Endangered and threatened wildlife and plants; removal of 21 species from the List of Endangered and Threatened Wildlife. Federal Register 88(199): 71644–71682.

  • U.S. Fish and Wildlife Service (USFWS). 2024. Environmental Conservation Online System. https://ecos.fws.gov/ecp/ (accessed on 08 May 2024).

  • van Riper, C., III, and M.J. Scott. 1979. Observations on distribution, diet and breeding of the Hawaiian Thrush. The Condor 81: 65–71.

  • van Riper, C., III, S.G. van Riper, M.L. Goff, and M. Laird. 1986. The Epizootiology and Ecological significance of malaria in Hawaiian land birds. Ecological Monographs 56(4): 327–344.

  • VanderWerf, E.A. 2001. Rodent control decreases predation on artificial nests in Oʻahu ʻElepaio habitat. Journal of Field Ornithology 72: 448–457.

  • VanderWerf, E.A. 2009. Importance of nest predation by alien rodents and avian poxvirus in conservation of Oahu ʻElepaio. Journal of Wildlife Management 73(5): 737–746.

  • VanderWerf, E.A., M.D. Burt, J.L. Rohrer, and S.M. Mosher. 2006. Distribution and prevalence of mosquito-borne diseases in Oʻahu ʻElepaio. The Condor 108(4): 770–777.

  • VanderWerf, E.A., R.E. David, P. Donaldson, R. May, H.D. Pratt, P. Pyle, and L. Tanino. 2018. First report of the Hawaiʻi Bird Records Committee. Western Birds 49(1): 2–23.

  • VanderWerf, E.A., S.M. Mosher, M.D. Burt, P.E. Taylor, and D. Sailer. 2011. Variable efficacy of rat control in conserving Oahu ʻElepaio populations. Pages 124–130 in C.R. Veitch, M.N. Clout, and D.R. Towns, editors. Island invasives: eradication and management. IUCN, Gland, Switzerland.

  • Vaughn, N.R., R.F. Hughes, and G.P. Asner. 2023. Multi-scale remote sensing-based landscape epidemiology of the spread of Rapid ’Ōhiʻa Death in Hawaiʻi. Forest Ecology and Management 538: 120983.

  • Vizentin-Bugoni, J., C.E. Tarwater, J.T. Foster, D.R. Drake, J.M. Gleditsch, A.M. Hruska, J.P. Kelley, and J.H. Sperry. 2019. Structure, spatial dynamics, and stability of novel seed dispersal mutualistic networks in Hawaiʻi. Science 364(6435): 78–82.

  • Warner, R.E. 1968. The role of introduced diseases in the extinction of the endemic Hawaiian avifauna. The Condor 70(2): 101–120.

  • Walther, M., and J.P. Hume. 2016. Extinct birds of Hawaiʻi. Mutual Publishing, Honolulu, Hawaiʻi.

  • Witmer, G.W., and A.B. Shiels. 2017. Ecology, impacts, and management of invasive rodents in the United States. Pages 193–219 in W.C Pitt, J.C. Beasley, and G.W. Witmer, editors. Ecology and Management of Terrestrial Vertebrate Invasive Species in the United States. CRC Press, Boca Raton, Florida.

  • Wolfe, E.W., and J. Morris. 1996. Geologic map of the island of Hawaiʻi. USGS Miscellaneous Investigations Series Map I-2524-A. https://doi.org/10.3133/i2524A

  • Woodworth, B.L., C.T. Atkinson, D.A. LaPointe, P.J. Hart, C.S. Spiegel, E.J. Tweed, C. Henneman, J. LeBrun, T. Denette, R. DeMots, and K.L. Kozar. 2005. Host population persistence in the face of introduced vector-borne diseases: Hawaiʻi ʻamakihi and avian malaria. Proceedings of the National Academy of Sciences 102(5): 1531–1536. https://doi.org/10.1073/pnas.0409454102

  • Zheng, X., D. Zhang, Y. Li, C. Yang, Y. Wu, X. Liang, Y. Liang, X. Pan, L. Hu, Q. Sun, X. Wang, Y. Wei, J. Zhu, W. Qian, Z. Yan, A.G. Parker, et al. 2019. Incompatible and sterile insect techniques combined eliminate mosquitoes. Nature 572(7767): 56–61.

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Appendix. Landbird Occurrence Maps

Occurrence maps for every landbird species detected during the 2020 and 2021 survey of Hawaiʻi Volcanoes National Park (HAVO) are presented in Figures 9–54 below.

Figure 9. Map of the Kahuku tracts showing African Silverbill detections only in Mauna Loa South Flank, where a handful of stations along the main transect carry small red circles for 1–3 birds per count. This grass‑associated finch is present but uncommon and limited to the south‑flank pasture–woodland mosaic.
Figure 9. African Silverbill detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

“Figure
Figure 10. American Barn Owl detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

”Figure
Figure 11. ʻApapane detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 12. Map of the Kahuku tracts showing ʻApapane detections, with dense red circles at most stations in Honomalino and Pāpā and along the Mauna Loa South Flank transect, and a smaller cluster in Northwest Kahuku. Larger circles indicate up to 9–14 birds per count in the leeward tracts, whereas Northwest Kahuku shows a mix of smaller symbols and blank stations, highlighting that ʻApapane are abundant and widespread in mid‑elevation forests but occur more patchily in higher, drier habitat.
Figure 12. ʻApapane detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

”Figure
Figure 13. California Quail detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 14. Map of the Kahuku tracts showing California Quail detections at multiple stations in Northwest Kahuku, marked by red circles scaled for 0.5–3 birds per count. The other tracts (Honomalino, Pāpā, Mauna Loa South Flank) show only unsupplemented black station dots, indicating absence during surveys and suggesting that California Quail are localized to the higher, open habitats of Northwest Kahuku.
Figure 14. California Quail detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 15. Map of the old park tracts showing Chinese Hwamei detections at several stations along Mauna Loa Strip and in the East Rift Zone sampling frame, with red circles indicating 1–2 birds per count, and no detections in ʻŌlaʻa. The pattern suggests that this introduced songbird is associated mainly with drier forest and edge habitats along the strip and lower East Rift Zone, with no use of the wetter ʻŌlaʻa forest during surveys.
Figure 15. Chinese Hwamei detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 16. Map of the old park tracts showing Common Myna detections at one station in the Mauna Loa Strip and one station in the ʻŌlaʻa sampling frame, each marked by a small red circle for one bird per count. All remaining stations, including those in the East Rift Zone, lack symbols, indicating that this urban‑associated species occurred only sporadically along forest edges near the park boundary.
Figure 16. Common Myna detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 17. Map of the old park tracts showing Common Waxbill detections at a few stations in the Mauna Loa Strip sampling frame, with red circles indicating 2–3 birds per count, and no detections in ʻŌlaʻa or the East Rift Zone. The limited cluster along the strip suggests that this introduced grassland finch is present but localized to open pasture–shrub habitats bordering the road corridor.
Figure 17. Common Waxbill detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 18. Map of the Kahuku tracts showing Common Waxbill detections only in Mauna Loa South Flank, where a handful of stations along the main transect carry small red circles for 1–3 birds per count. Stations in Northwest Kahuku, Honomalino, and Pāpā are shown without red overlays, illustrating that this grass‑associated finch is present but uncommon and limited to the south‑flank pasture–woodland mosaic.
Figure 18. Common Waxbill detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 19. Map of the old Hawaiʻi Volcanoes National Park survey tracts showing Erckel’s Spurfowl detections as numerous red circles along transects in the Mauna Loa Strip sampling frame, with circle sizes indicating up to four birds per count and no detections in ʻŌlaʻa or the East Rift Zone. The concentration of symbols in the strip highlights that this introduced gamebird is common and locally abundant in higher‑elevation grass–shrub and open woodland habitats, but absent from wetter forest tracts in the old HAVO area
Figure 19. Erckel’s Spurfowl detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 20. Map of the Hawaiʻi Volcanoes National Park survey Kahuku tracts showing Erckel’s Spurfowl detections as numerous red circles along transects in the Mauna Loa South Flank, Honomalino, Papa, and Northwest Kahuku sampling frames, with circle sizes indicating up to five birds per count. The concentration of symbols in the strip highlights that this introduced gamebird is common and locally abundant in higher‑elevation grass–shrub and open woodland habitats, but absent from lower elevation areas of the Mauna Loa South Flank area.
Figure 20. Erckel’s Spurfowl detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 21. Map of the Old HAVO tracts showing Eurasian Skylark detections confined to the Mauna Loa Strip tract, where a single station with a small red circle represents 1 bird per count. All stations in Olaa and East Rift Zone are symbolized only by black dots with no overlays, emphasizing that this open‑country passerine is restricted to high‑elevation subalpine grassland and sparse shrubland.
Figure 21. Eurasian Skylark detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 22. Map of the Kahuku tracts showing Eurasian Skylark detections confined to Northwest Kahuku, where several stations carry small red circles representing 1–2 birds per count. All stations in Honomalino, Pāpā, and Mauna Loa South Flank are symbolized only by black dots with no overlays, emphasizing that this open‑country passerine is restricted to high‑elevation subalpine grassland and sparse shrubland in the northwest tract.
Figure 22. Eurasian Skylark detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 23. Map of the old park tracts showing Hawaiʻi ʻAmakihi detections as dense red circles along all Mauna Loa Strip transects and at a few stations in the East Rift Zone, with circle sizes indicating up to about nine birds per count, and no detections in ʻŌlaʻa. This pattern shows that the native honeycreeper is abundant in drier high‑elevation forest and woodland along the strip, occurs at lower densities in the East Rift Zone, and was not detected in the wetter ʻŌlaʻa tract during surveys.”</p> <p><strong>Figure 23.</strong> Hawaiʻi ʻAmakihi detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.
Figure 23. Hawaiʻi ʻAmakihi detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 24. Map of the Kahuku tracts showing Hawaiʻi ʻAmakihi detections as dense red circles along all South Flank, Honomalino, Papa, and Northwest Kahuku transects indicating up to about eleven birds per count. This pattern shows that the native honeycreeper is abundant in drier high‑elevation forest and woodland.
Figure 24. Hawaiʻi ʻAmakihi detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 25. Map of the old park tracts showing Hawaiʻi ʻElepaio detections at multiple stations in both Mauna Loa Strip and ʻŌlaʻa sampling frames, symbolized by red circles for 1–3 birds per count, with no detections in the East Rift Zone. The distribution indicates that this native forest flycatcher is fairly common in mid‑ to high‑elevation native forest on the strip and in ʻŌlaʻa but absent from the more open and lower East Rift Zone transects.
Figure 25. Hawaiʻi ʻElepaio detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 26. Map of the Kahuku tracts showing Hawaiʻi ʻElepaio detections concentrated in the leeward Honomalino and Pāpā tracts, with several stations marked by red circles representing 1–7 birds per count, plus a single detection along the Mauna Loa South Flank transect and none in Northwest Kahuku. The pattern indicates that this native forest flycatcher is centered in lower‑elevation mesic forest, tapering off at higher elevations and on the more open south‑flank pasture.
Figure 26. Hawaiʻi ʻElepaio detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 27. Map of the old park tracts showing House Finch detections at scattered stations along Mauna Loa Strip, each marked by red circles representing 1–3 birds per count, and no detections in ʻŌlaʻa or the East Rift Zone. The localized symbols along the strip suggest that this introduced finch is present mainly in open woodland and road‑edge habitats at higher elevations, with no use of the wetter or more closed forests elsewhere in the old HAVO area.
Figure 27. House Finch detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

NPS

Figure 28. Map of the Kahuku tracts showing House Finch detections as dense clusters of red circles in Northwest Kahuku and along the Mauna Loa South Flank transect, with additional but fewer detections in Honomalino and Pāpā; circle size indicates up to 6–7 birds per count. The widespread, high‑density symbols in open and semi‑open tracts emphasize that this introduced finch is common across Kahuku, especially in higher‑elevation grass–shrub and pasture–woodland habitats.
Figure 28. House Finch detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 29. Map of the Kahuku tracts showing ʻIʻiwi detections limited to a cluster of stations in Honomalino and one station in Pāpā, marked by red circles scaled for 1–3 birds per count, with no detections in Northwest Kahuku or Mauna Loa South Flank. This pattern highlights that the native nectarivorous honeycreeper persists at low densities in select leeward forest patches but is absent from higher and more open habitats in the Kahuku Unit.
Figure 29. ʻIʻiwi detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 30. Map of the old park tracts showing ʻIo detections only in the ʻŌlaʻa sampling frame, where a few stations bear small red circles indicating one hawk per count. All Mauna Loa Strip and East Rift Zone stations lack symbols, highlighting that this native raptor was detected infrequently and only over the ʻŌlaʻa forest during the survey period.
Figure 30. ʻIo detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 31. Map of the Kahuku tracts showing ʻIo detections only along the Mauna Loa South Flank transect, where two or three stations bear small red circles for 1–2 hawks per count. All other tracts display only black station dots, indicating that this native raptor was detected infrequently and only over the open pasture–woodland habitats on the south flank during surveys.
Figure 31. ʻIo detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 32. Map of the old Hawaiʻi Volcanoes National Park tracts showing Japanese Bush Warbler detections at scattered stations in Mauna Loa Strip, ʻŌlaʻa, and the East Rift Zone, represented by red circles sized for up to about five birds per count. The symbols cluster along forested transects and road edges, indicating that this introduced understory songbird is fairly common across wetter and drier forest habitats but absent from some higher, more open portions of the strip.
Figure 32. Japanese Bush Warbler detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 33. Map of the Kahuku tracts showing Japanese Bush Warbler detections primarily at the lower Honomalino stations, with several red circles indicating up to four birds per count and only one or two small symbols in Pāpā and Northwest Kahuku. No detections occur on Mauna Loa South Flank, underscoring that this invasive understory songbird is most common in dense vegetation of the lower leeward tract and occurs sparsely elsewhere.
Figure 33. Japanese Bush Warbler detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 34. Map of the old park tracts showing Kalij Pheasant detections at a single station in the Mauna Loa Strip sampling frame, marked by a medium red circle indicating 2–3 birds per count, with no detections in ʻŌlaʻa or the East Rift Zone. The isolated symbol along the strip highlights that this introduced gamebird occurred rarely in higher‑elevation woodland and was not recorded in other tracts during surveys.”</p> <p><strong>Figure 34.</strong> Kalij Pheasant detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.
Figure 34. Kalij Pheasant detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 35. Map of the Kahuku tracts showing Kalij Pheasant detections at a few scattered stations in Honomalino, Pāpā, and Mauna Loa South Flank, each symbolized by small red circles for 1–2 birds per count, with no detections in Northwest Kahuku. This distribution suggests that Kalij Pheasants are present at low densities in mid‑elevation forest and pasture habitats but absent from the highest, more exposed northwest tract during the survey period.
Figure 35. Kalij Pheasant detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 36. Map of the Kahuku tracts showing Nēnē detections only at two adjacent stations along the Mauna Loa South Flank transect, symbolized by a small red circle for one bird and a larger circle for six birds per count, with no detections in Northwest Kahuku, Honomalino, or Pāpā. This pattern indicates that the native goose was encountered rarely and exclusively in open pasture–woodland habitat on the south flank during surveys.
Figure 36. Nēnē detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 37. Map of the old park tracts showing Northern Cardinal detections as numerous red circles along transects in Mauna Loa Strip and in the East Rift Zone, with additional symbols in ʻŌlaʻa; circle sizes indicate up to four birds per count. The wide spread of symbols across all three sampling frames underscores that this introduced songbird is common and broadly distributed from upper‑elevation woodland to lower forest and edge habitats in the old HAVO area.
Figure 37. Northern Cardinal detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 38. Map of the Kahuku tracts showing Northern Cardinal detections as numerous red circles across Northwest Kahuku, Honomalino, Pāpā, and along the Mauna Loa South Flank transect, with circle sizes indicating up to four birds per count. The widespread coverage of symbols over most landbird stations highlights that this introduced songbird is common and broadly distributed from lower leeward forests to higher‑elevation pasture and shrub habitats in the Kahuku Unit.
Figure 38. Northern Cardinal detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 39. Map of the Kahuku tracts showing Northern Mockingbird detections confined to Northwest Kahuku, where a cluster of stations bears red circles representing 1–3 birds per count. All stations in Honomalino, Pāpā, and Mauna Loa South Flank lack red overlays, emphasizing that this species is locally common in the high‑elevation grass–shrub mosaic of the northwest tract and absent elsewhere in Kahuku.
Figure 39. Northern Mockingbird detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected

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Figure 40. Map of the old park tracts showing ʻŌmaʻo detections concentrated along Mauna Loa Strip, East Rift Zone, and ʻŌlaʻa tracts, where many stations bear red circles representing 1–4 birds per count.. This pattern indicates that the native thrush is common in mid‑ to high‑elevation native forest within the Old HAVO Unit.
Figure 40. ʻŌmaʻo detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 41. Map of the Kahuku tracts showing ʻŌmaʻo detections only along the Mauna Loa South Flank transect, where a vertical line of stations carries red circles scaled for 1–2 birds per count. No symbols appear in Northwest Kahuku, Honomalino, or Pāpā, indicating that this native thrush was detected solely in south‑flank forest–pasture habitat and was absent from the leeward and higher‑elevation tracts during surveys.
Figure 41. ʻŌmaʻo detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 42. Map of the Kahuku tracts showing a single Pueo detection in Northwest Kahuku, marked by one small red circle at an upper‑elevation station. The remaining stations across all tracts are shown only as black dots, underscoring that this native owl was detected just once and only in open subalpine habitat during the survey period.
Figure 42. Pueo detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 43. Map of the old park tracts showing Red‑billed Leiothrix detections at many stations in Mauna Loa Strip and ʻŌlaʻa, with red circles scaled for 1–4 birds per count, and no detections in the East Rift Zone. The dense clusters of symbols in both forested tracts show that this introduced understory songbird is widespread and fairly abundant in native forest but was not recorded in the more open East Rift Zone.
Figure 43. Red-billed Leiothrix detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 44. Map of the Kahuku tracts showing Red‑billed Leiothrix detections scattered mainly through Honomalino and Pāpā, with red circles at several stations indicating up to three birds per count, plus a few detections on Mauna Loa South Flank and none in Northwest Kahuku. The concentration in lower leeward tracts suggests that this introduced understory songbird is most common in mid‑elevation forest, with lower densities in more open south‑flank habitats and absence from the high, exposed northwest tract.
Figure 44. Red-billed Leiothrix detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 45. Map of the old park tracts showing Scaly‑breasted Munia detections at a single station in Mauna Loa Strip, marked by one red circle indicating two birds per count, with no detections in ʻŌlaʻa or the East Rift Zone. The lone symbol along the strip suggests that this introduced granivorous finch occurred only once in open grass–shrub or roadside habitat during the survey period.
Figure 45. Scaly-breasted Munia detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 46. Map of the Kahuku tracts showing Scaly‑breasted Munia detections at a single station along the Mauna Loa South Flank transect, marked by one small red circle representing one bird per count. All other stations in Northwest Kahuku, Honomalino, and Pāpā lack symbols, indicating that this introduced granivorous finch was recorded only once and solely in south‑flank pasture–woodland habitat during surveys.
Figure 46. Scaly-breasted Munia detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 47. Map of the old park tracts showing Spotted Dove detections at one station in Mauna Loa Strip and one station in ʻŌlaʻa, each symbolized by a small red circle for one bird per count, and no detections in the East Rift Zone. The sparse, isolated symbols indicate that this introduced dove is uncommon and occurs only sporadically along forest edges near roads within the old HAVO area.
Figure 47. Spotted Dove detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 48. Map of the old park tracts showing Warbling White‑eye detections as dense red circles at nearly all stations in Mauna Loa Strip, ʻŌlaʻa, and the East Rift Zone, with symbol sizes indicating up to about 14–18 birds per count. The heavy coverage of large circles across all sampling frames demonstrates that this introduced songbird is extremely abundant and ubiquitous in forest, woodland, and edge habitats throughout the old HAVO area.
Figure 48. Warbling White-eye detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 49. Map of the Kahuku tracts showing Warbling White‑eye detections as numerous red circles across Honomalino, Pāpā, Northwest Kahuku, and especially along the Mauna Loa South Flank transect, with circle sizes indicating up to 7–8 birds per count. The dense coverage of symbols over nearly all stations demonstrates that this small introduced passerine is one of the most abundant and widespread landbirds across all habitats in the Kahuku Unit.
Figure 49. Warbling White-eye detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 50. Map of the Kahuku tracts showing Wild Turkey detections at a few stations clustered in Northwest Kahuku, symbolized by small and medium red circles for 1–3 birds per count. Stations in Honomalino, Pāpā, and Mauna Loa South Flank lack overlays, indicating that this large gamebird occurs only in the high‑elevation grass–shrub mosaic of the northwest tract during surveys.
Figure 50. Wild Turkey detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 51. Map of the old park tracts showing a single Yellow‑billed Cardinal detection at one station in the East Rift Zone sampling frame, represented by a small red circle indicating one bird per count, with no detections in Mauna Loa Strip or ʻŌlaʻa. This solitary symbol along the lower‑elevation transect indicates that this introduced cardinal was recorded only once and solely in open or edge habitat of the East Rift Zone.
Figure 51. Yellow-billed Cardinal detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 52. Map of the old Hawaiʻi Volcanoes National Park tracts showing Yellow‑fronted Canary detections at several stations along Mauna Loa Strip and at a few stations in the East Rift Zone, represented by red circles sized for 1–3 birds per count, with no detections in ʻŌlaʻa. The clustering of symbols along upper‑elevation roadside transects and in lower‑elevation East Rift grass–shrub areas indicates that this introduced seedeater is locally common in open and edge habitats but absent from the wetter ʻŌlaʻa forest during surveys.
Figure 52. Yellow-fronted Canary detections within the Old HAVO Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 53. Map of the Kahuku tracts showing Yellow‑fronted Canary detections at one station in Honomalino and several stations along the Mauna Loa South Flank transect, with red circles scaled up to four birds per count on the south flank. The absence of symbols in Northwest Kahuku and Pāpā highlights that this introduced seedeater is localized to lower leeward forest–pasture and especially common in open grass–shrub habitats on the south flank.
Figure 53. Yellow-fronted Canary detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Figure 54. Map of the Kahuku tracts showing Zebra Dove detections at a single station in the Honomalino tract, marked by one small red circle indicating one bird per count. All other stations in Northwest Kahuku, Pāpā, and Mauna Loa South Flank appear only as black dots, indicating that this introduced dove was detected just once and only in lower leeward pasture–forest habitat during surveys.
Figure 54. Zebra Dove detections within the Kahuku Unit during the 2020–2021 Hawaiʻi Volcanoes National Park landbird survey. The number of birds per station was divided by the number of counts at each station where species was detected.

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Author Information

Seth W. Judge 1

Kristina L. Paxton 2

Angela T. Beck 3

Richard J. Camp 4

1 National Park Service
Pacific Island Inventory and Monitoring Network
Hawaiʻi National Park, HI 96718

2 University of Hawaiʻi at Hilo
Hawaiʻi Cooperative Studies Unit
200 W. Kāwili St.
Hilo, HI 96720

3 University of Hawaiʻi at Hilo
Research Corporation for the University of Hawaiʻi
200 W. Kāwili St.
Hilo, HI 96720

4 United States Geological Survey
Pacific Island Ecosystems Research Center
P.O. Box 44
Hawaiʻi National Park, HI 96718

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