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Hawaii — Our Liviiit; Resources 



Hawaii's 

 Endemic Birds 



by 



James D. Jacobi 



Carter T. Atkinson 

 National Biological Ser\'ice 



Fig. 1. Current status of endemic 

 Hawaiian bird species known to 

 exist at the time of Western con- 

 tact (1778). 



The endemic landbirds of Hawaii, particular- 

 ly the Hawaiian honeycreepers. an endemic 

 subfamily of the cardueline finches, are one of 

 the world's most dramatic examples of adaptive 

 radiation and speciation (see glossary) in island 

 ecosystems (Freed et al. 1987; Scott et al. 

 1988). From what is believed to have been a sin- 

 gle successful colonization of the Hawaiian 

 Archipelago by an ancestral species from North 

 America, the honeycreepers evolved into a 

 diverse array of species and subspecies of birds 

 with bills ranging from thick, seed-eating beaks 

 of the palila (Loxioides bailleiii), to small insec- 

 tivorous bills as seen on the "amakihi 

 (HemigiuitliHs vireiis). woodpecker-like adapta- 

 tions of the 'akiapola'au (//. mimnn). and large, 

 decurved nectar-feeding bills of the "iMvvi 

 ( Vestiaria coccinea). 



In addition to the honeycreepers, the histoii- 

 cally documented endemic Hawaiian avifauna 

 included three seabirds, several waterfowl, two 

 raptors, and perching birds that include a 

 species of crow, and representatives of Old 

 World flycatchers, honeyeaters. and thrushes. In 

 all, at least 71 endemic species and subspecies 

 of Hawaiian birds existed at the time of Captain 

 Cook's anival in the Hawaiian Islands in 1778. 

 Now, however, 76% of the Hawaiian birds are 

 either extinct or endangered, and several of the 

 remaining unlisted species are showing signifi- 

 cant population declines. 



The arrival of humans to the Hawaiian 

 Islands — starting with the Polynesians more 

 than 1,500 years ago and continuing following 

 European contact— drastically changed many 

 natural ecosystems, leading not only to the 

 extinction of many plant and animal species, but 

 also to a significant reduction in both range and 

 abundance for many other taxa. Originally, the 

 Hawaiian birds were found in all habitat zones 

 on each island, but today few native forest birds 

 are found below 610-m (2.000-ft) elevation, and 

 many of the wetland areas that once provided 

 abundant habitat for waterbirds have been 

 destroyed. 



Of the historically documented 71 taxa of 

 endemic Hawaiian birds, 23 are now extinct, 

 and 30 of the remaining 48 species and sub- 

 species are listed as endangered or threatened 

 by the U.S. Fish and Wildlife Service (USFWS 

 1992), many with few or only single popula- 

 tions remaining (Fig. I; Table I: Table 2). 

 Studies of recently discovered fossil bird bones 

 have further identified nearly 40 addidonal 

 species of Hawaiian birds never seen alive by 

 the post-Cook naturalists: many of these 

 became extinct after the Polynesians arrived 

 (Olson and James 1982; H. James. Smithsonian 

 Institution, personal communication). 



Table 1. Historically known endemic Hawaiian birds that 

 are now extinct. 



Reasons for the Decline 



Many factors have been suggested to explain 

 the decline of Hawaiian bird species since 

 human colonization (Ralph and van Riper 1985; 

 Scott et al. 1988). The most important and plau- 

 sible of these include habitat loss (Berger 1981; 

 Kirch 1982; Olson and James 1982; Jacobi and 

 Scott 1985), susceptibility to introduced avian 

 diseases (Warner 1968; Ralph and van Riper 

 1985; van Riper et al. 1986). predation by intro- 

 duced mammals (Atkinson 1977). and competi- 

 tion from introduced birds (Mountainspring and 

 Scott 1985) and arthropods (Perkins 1903; 

 Banko and Banko 1976). Although no one fac- 

 tor is believed to be the single cause for the loss 

 or decline of the Hawaiian birds, many biolo- 

 gists believe that habitat loss and avian diseases 

 have had the greatest effect on native birds. 



Habitat Loss 



Habitat loss from forest removal and devel- 

 opment in the Hawaiian Islands started when 

 large tracts of mostly lower elevation land were 

 cleared for agriculture by the first Hawaiian 

 colonists. After European and American settlers 

 anived. starting in the late 1 8th century, habitat 

 loss increased dramatically as agriculture and 

 ranching expanded. Today, less than 40% of the 

 land surface of Hawaii is covered with native- 

 dominated vegetation (Jacobi 1990; S. Gon, 

 The Nature Conservancy of Hawaii, unpub- 

 lished data). Some of the most significant loss 

 of habitat has occurred below 610 m (2,000 ft) 



