Population estimates and trends of three Maui Island‐endemic Hawaiian Honeycreepers

Population monitoring is critical for informing the management and conservation of rare Hawaiian forest birds. In 2017, we used point‐transect distance sampling methods to estimate population densities of birds on Haleakalā Volcano on east Maui island. We estimated the populations and ranges of three island‐endemic Hawaiian honeycreepers, including the endangered ‘Ākohekohe (Palmeria dolei), the endangered Kiwikiu (Maui Parrotbill; Pseudonestor xanthophrys), and the Maui ʻAlauahio (Paroreomyza montana newtoni). We examined population trends back to 1980, and our 2017 density estimates were the lowest ever recorded for each species. Most concerning was the status of Kiwikiu, with a 71% decline in population since 2001 to a current population of 157 (95% CI 44–312) birds. The population of ‘Ākohekohe similarly decreased by 78% to a current population of 1768 (1193–2411) birds. For both species, population declines were due to declines in density and contraction of ranges from lower elevations. Both species are now restricted to ranges of less than 3000 ha. We surveyed ~ 91% of the range of Maui ‘Alauahio and estimated a population of 99,060 (88,502–106,954) birds, a 41% decrease since the highest estimate in 1992. Contraction of ranges to higher elevations is consistent with evidence that the impacts of avian malaria are being exacerbated by global warming trends. Our results indicate that the landscape control of either avian malaria transmission or its vector (Culex mosquitoes) will be a pre‐requisite to preventing the extinction of endemic forest birds in Hawaii. RESUMEN Estimaciones y tendencias poblacionales de tres especies endémicas de trepadores de miel hawaianos en la isla de Maui El monitoreo poblacional es fundamental para informar sobre la gestión y la conservación de aves forestales raras aves de Hawai. En 2017, utilizamos métodos de muestreo de distancia de transectos puntuales para estimar las densidades de población de aves en el volcán Haleakalā en la isla este de Maui. Estimamos las poblaciones y áreas de distribución de tres trepadores de miel hawaianos endémicos de la isla, incluido la especie en peligro de extinción ‘Ākohekohe (Palmeria dolei), la especie en peligro de extición Kiwikiu (Pico de loro de Maui; Pseudonestor xanthophrys) y el Alauahio de Maui (Paroreomyza montana newtoni). Examinamos las tendencias de la población desde 1980, y nuestras estimaciones de densidad de 2017 fueron las más bajas jamás registradas para cada especie