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1 May 2010 Population Trends of Forest Birds at Hakalau Forest National Wildlife Refuge, Hawai'i
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Abstract

The Hakalau Forest National Wildlife Refuge was established to protect native Hawaiian forest birds, particularly endangered species. Management for forest restoration on the refuge has consisted mainly of removing feral ungulates, controlling invasive alien plants, and reforesting former pastures. To assess effects of this habitat improvement for forest birds, we estimated density annually by distance sampling and examined population trends for native and alien passerines over the 21 years since the refuge was established. We examined long-term trends and recent short-term trajectories in three study areas: (1) reforested pastureland, (2) heavily grazed open forest that was recovering, and (3) lightly grazed closed forest that was relatively intact. Three species of native birds and two species of alien birds had colonized the reforested pasture and were increasing. In the open forest, densities of all eight native species were either stable or increasing. Long-term trends for alien birds were also generally stable or increasing. Worryingly, however, during the most recent 9 years, in the open forest trajectories of native species were decreasing or inconclusive, but in the reforested pasture they generally increased. The closed forest was surveyed in only the most recent 9 years, and trajectories of native species there were mixed. Overall, long-term population trends in Hakalau are stable or increasing, contrasting with declines in most other areas of Hawai'i over the same period. However, more recent mixed results may indicate emergent problems for this important bird area.

© 2010 by The Cooper Ornithological Society, All rights reserved, Please direct all requests for permission to photocopy or reproduce article content through the University of California Press's Rights and Permissions website, http://www.ucpressjournals.com/reprintInfo.asp.
Richard J. Camp, Thane K. Pratt, P. Marcos Gorresen, John J. Jeffrey, and Bethany L. Woodworth "Population Trends of Forest Birds at Hakalau Forest National Wildlife Refuge, Hawai'i," The Condor 112(2), (1 May 2010). https://doi.org/10.1525/cond.2010.080113
Received: 19 December 2008; Accepted: 1 October 2009; Published: 1 May 2010
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