Pacific Island landbird monitoring report, Kalaupapa National Historical Park, 2021

In 2021, landbird surveys were conducted at Kalaupapa National Historical Park on the island of Molokaʻi to assess changes in species composition, distribution, and population densities since 2005. Point-transect distance sampling surveys were conducted on six transects at 50 landbird monitoring stations within an 1,834-hectare area. A total of nine landbird species were detected, with the ʻApapane (Himatione sanguinea) the only endemic Hawaiian species detected. Sufficient detections of six species allowed for population density and abundance estimates, which were compared to 2005 estimates using a two-sample z-test. The abundance of ʻApapane declined by 57% to 2,476 ± 729 (SE) birds in 2021 compared to 2005. Population densities of the House Finch (Haemorhous mexicanus), Japanese Bush Warbler (Horornis diphone), Warbling White-eye (Zosterops japonicus), and White-rumped Shama (Copsychus malabaricus) were also lower in 2021 than in 2005, but comparisons were inconclusive. Since 2005, the Red-billed Leiothrix (Leiothrix lutea) irrupted within the survey area to an estimated abundance of 11,088 ± 1,208 birds. The Warbling White-eye was the most abundant species, with an estimated 101,724 ± 11,692 birds. Surveyors failed to detect the Hawaiʻi ʻAmakihi (Chlorodrepanis virens), which has become increasingly rare on Molokaʻi. The federally threatened ʻIʻiwi (Drepanis coccinea) was last seen on Molokaʻi in 2010, further raising concerns about its potential extirpation. The Olomaʻo (Myadestes lanaiensis), an endemic thrush, has not been detected since 1980 and is likely extinct. These findings show the ongoing shift toward non-native bird communities and highlight the challenges of conserving native forest birds amidst widespread avian malaria transmission, introduced predators, and extensive habitat degradation.