Pacific island landbird monitoring annual report, Haleakalā National Park and East Maui Island, 2017

Judge, Seth; Camp, Richard; Warren, Christopher; Berthold, Laura; Mounce, Hanna; Hart, Patrick; Monello, Ryan

In 2017, the National Park Service Inventory and Monitoring Program, Maui Forest Bird Recovery Project, Pacific Cooperative Studies Unit, State of Hawai‘i Division of Forestry and Wildlife, and the United States Geological Survey, along with several other partners, coordinated and conducted a broad-scale landbird survey on East Maui Island, including portions of Haleakalā National Park (HALE). This survey marks the first interagency effort to collaboratively survey the entire set of East Maui forest bird survey transects since 1980 and provides data for the monitoring of long-term trends in distribution, density, and abundance of landbird species. The survey area encompassed approximately 146 km2 of Haleakalā Volcano and was divided into four regions: HALE, Leeward, Kula, and Windward. A total of 32 transects were surveyed using point-transect distance sampling methods, and audio recorders were deployed in HALE to supplement survey efforts. Sufficient detections to allow for density estimation were made for ten species (six native and four non-native). We used a two-sample z-test to check for short-term differences in density between our 2017 efforts and the most recent surveys in the HALE (2012) and Windward (2011) Regions. We also determined global population estimates and ranges of the three remaining island-endemic honeycreepers: the endangered Kiwikiu (Maui Parrotbill; Pseudonestor xanthophrys), the endangered ‘Ākohekohe (Crested Honeycreeper; Palmeria dolei); and the Maui ʻAlauahio (Maui Creeper; Paroreomyza montana newtoni). Surveyors detected a total of 13,502 birds of 27 species. Within the survey area, the most abundant species were the native ‘Apapane (Himatione sanguinea; 228,480 ± 19,855 SE) and non-native Japanese White-eye (Zosterops japonicus; 127,560 ± 6,544). The two least abundant species were the Kiwikiu (157 ± 67) and ‘Ākohekohe (1,768 ± 315), both species are endemic to Maui Island and only occur within the 2017 survey area. Most tests for differences in density between 2011/12 and 2017 in HALE and Windward Regions were inconclusive due to the relatively small difference and large uncertainty in the density estimates associated with only two sample points in time. However, there were some localized changes in landbird densities within their range on East Maui. Among native species, the threatened ‘I‘iwi (Drepanis coccinea) density increased in the Windward Region, Hawaiʻi ‘Amakihi (Chlorodrepanis virens) density decreased in HALE and Windward Regions, and Kiwikiu density decreased in HALE. Densities of the non-native Japanese Bush-Warbler (Horornis diphone) and Red-billed Leiothrix (Leiothrix lutea) were found to be increasing in the Windward Region. All three island-endemic species were found to have declined in abundance by 50% or more over the last 20–35 years. Most concerning is the trend of Kiwikiu; although this species has always had relatively low global population estimates. Our estimate of 157 ± 67 is substantially lower than the prior global estimate of 513 ± 143 made in 1980. Low abundance was accounted by low population density as well as a 27% decline in range. Similarly, range of ‘Ākohekohe declined by 61% and range-wide densities were the lowest ever recorded. In both cases, ranges contracted at lower elevations where both species regularly occurred only 10–15 years ago. Finally, Maui ʻAlauahio abundance also declined by 50% over the last two decades, but in this case it was primarily due to a decline in density, as the species still occupies much of its previously estimated range.

Pacific island landbird monitoring annual report, Haleakalā National Park and East Maui Island, 2017

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