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1 March 2001 CURRENT DISTRIBUTION AND ABUNDANCE OF THE O‘AHU ‘ELEPAIO
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Abstract
The O‘ahu ‘Elepaio (Chasiempis sandwichensis ibidis) is a monarch flycatcher endemic to the Hawaiian island of O‘ahu. This forest bird has declined seriously in the last few decades and was listed as endangered under the federal Endangered Species Act in April 2000. The current distribution and population size of the O‘ahu ‘Elepaio are poorly known, and this information is vital to designing a recovery plan and implementing recovery actions. We surveyed most of O‘ahu for ‘Elepaio from 1992–2000 and compiled published and unpublished observations to estimate the current population size and construct current, recent historical, and prehistoric distribution maps. Based on 411 observations since 1991, we estimate the current population to be 1974 birds in six large subpopulations and several smaller ones. The breeding population consists of about 1768 birds due to a male-biased sex ratio, and the genetically effective population size is even lower because of the fragmented distribution. Total area of the current range is approximately 5486 ha, only 4% of the prehistoric range, and 25% of the range in 1975. Habitat loss to urbanization and agriculture caused large range reductions in the past, but cannot explain more recent declines. ‘Elepaio disappeared first from areas of higher rainfall, possibly because epizootics of introduced mosquito-borne diseases are more frequent where wetter conditions provide more mosquito breeding habitat. Management is urgently needed to prevent further declines and extirpation of smaller subpopulations.
Eric A. VanderWerf, JOBY L. ROHRER, David G. Smith and MATTHEW D. BURT "CURRENT DISTRIBUTION AND ABUNDANCE OF THE O‘AHU ‘ELEPAIO," The Wilson Bulletin 113(1), (1 March 2001). https://doi.org/10.1676/0043-5643(2001)113[0010:CDAAOT]2.0.CO;2
Received: 17 August 2000; Accepted: 1 January 2001; Published: 1 March 2001
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