Forest bird populations at the Pu‘u Wa‘a Wa‘a Forest Bird Sanctuary and Pu‘u Wa‘a Wa‘a Forest Reserve, Hawai‘i

Abstract

Endemic Hawaiian forest birds have exhibited dramatic population declines since human colonization of Hawai‘i. The Pu‘u Wa‘awa‘a Forest Bird Sanctuary and adjacent Pu‘u Wa‘awa‘a Forest Reserve on Hawai‘i Island were established in 2002 to conserve endemic forest birds and their habitats. Surveys have been conducted in this area to monitor forest bird populations and their response to management actions since 1979. We analyzed point-transect distance sampling survey data collected between 1990 and 2022 in the Pu‘u Wa‘awa‘a Forest Bird Sanctuary and forested portions of the adjacent forest reserve. There were 20 passerine or psittacine species detected of which 6 were native species and 14 were non-native species. In all years, Hawai‘i ‘amakihi (Chlorodrepanis virens virens), ‘apapane (Himatione sanguinea), and warbling white-eye (Zosterops japonicus) were the most abundant species, and in most years ‘i‘iwi (Drepanis coccinea) was the fourth most abundant species. ‘I‘iwi and Hawai‘i ‘amakihi had stable long-term (1990–2022) population trends, and trends for ‘apapane were inconclusive, while warbling white-eye had upward trends. In recent years (2016–2022), ‘apapane had downward trends, ‘i‘iwi and warbling white-eye had upward trends, and trends for ‘amakihi were inconclusive. Populations of Hawai‘i ‘elepaio (Chasiempis sandwichensis) and the endangered Hawai‘i ‘ākepa (Loxops coccineus) and ‘alawī (Loxops mana) were either locally extirpated or in numbers too low to reliably estimate population densities and trends. The Pu‘u Wa‘awa‘a Forest Bird Sanctuary and adjacent Pu‘u Wa‘awa‘a Forest Reserve are important for the conservation of forest birds on Hawai‘i Island as one of few areas of mesic to dry forests being specifically managed for forest bird conservation. Conservation efforts at the Pu‘u Wa‘awa‘a Forest Bird Sanctuary and Pu‘u Wa‘awa‘a Forest Reserve would benefit from continued annual surveys and regular monitoring, and timely analysis of survey data to track responses in forest bird populations to evaluate and adapt management actions.