.m) 



Hawau — Oiir Living Resi}i<iccs 



Fig. 2. Summary of status of 

 endemic forest birds on the major 

 Hawaiian Islands. 



25 



^' Not endangered 



■i Endangered 



■ Extinct I^^H 



g 15 ^H 



■mil 



Hawaii thrush (M. obscunis) has relatively 

 rdhust populations on the windward side of the 

 island of Hawaii, but is extiipated in the wet 

 forests of both the leeward (Kona) side of the 

 island and in the Kohala region. 



Conservation Outlook 



While the prospects for survival of all 

 remaining Hawaiian bird species appear limit- 

 ed, conservation efforts to further the chances of 

 survival of even some of the rarest species can 

 be enhanced by using techniques such as 

 translocation, predator and disease vector con- 

 trol, and captive propagation in conjunction 

 with habitat-management prt^grams. 



Kajai 



Oahu 



Lanai Molokai 



Maul 



Hawaii Avian Disease Research and Management 



In addition to the waterhirds, the two rail 

 species endemic to Hawaii are now extinct. One 

 species, the Laysan rail (Porzana palineri). 

 known only from Laysan Island, became extinct 

 after introduced rabbits nearly totally defoliated 

 this small atoll in the early IQOO's (Berger 

 1 98 1 ). The other rail species endemic to Hawaii 

 [P. samhvichcnsis) was extremely rare in the 

 late 17(J0's when Western naturalists first began 

 to document the Hawaiian birds. This species 

 was probably extinct by the early 1900"s 

 (Berger 1981). 



Forest Birds 



Forest birds constitute the largest group of 

 Hawaiian birds, with 60 species and subspecies 

 described since Western contact. Several 

 species of passerines known from the 

 Northwest Hawaiian Islands are also included 

 with the forest bird group, although none of 

 these atolls has any forest habitat. 



Both the greatest number of species and the 

 number of losses of species of Hawaiian birds 

 are found in the forest bird group. Of 60 endem- 

 ic species and subspecies of Hawaiian forest 

 birds, 22 are believed extinct, an additional 23 

 are endangered or threatened (USFWS 1992), 

 and 4 are candidate species for listing (Table 2). 

 Thirteen of the endangered forest birds have 

 estimated populations of less than 50 individu- 

 als; 10 of these species have not been sighted 

 during the past 10 years and may be extinct. The 

 island of Kauai, which seemed to be the only 

 island with all historically known bird species 

 still extant, now has five species that may be 

 extinct (Fig. 2). Surveys in 199.3 and 1994 

 resulted in finding only one of the endangered 

 forest bird species, the puaiohi or small Kauai 

 thrush (Myadestes palineri). 



Only 1 1 Hawaiian forest bird taxa are con- 

 sidered relatively stable, but several populations 

 of these species, particularly the iiwi, have 

 experienced recent declines. The "oma'o or 



Since 1992 the National Biological Service's 

 disease studies have focused on determining the 

 effect of pox and malaria transmission on the 

 island of Hawaii and whether significant 

 changes in the prevalence and distribution of 

 these diseases have occuned since van Riper 

 and colleagues completed their work in the late 

 1970"s. Major new efforts to develop strategies 

 for monitoring transmission of these diseases in 

 remote forest habitats and for controlling vector 

 populations are in progress. 



In 1992 NBS scientists witnessed a major 

 pox and malaria epidemic in midelevation for- 

 est birds on the island of Hawaii. These birds 

 are highly susceptible to malaria. Results of 

 experimental infections with isolates of malaria 

 from wild birds demonstrated that a minimal 

 infective dose, equivalent to the bite of a single 

 malaria-infected mosquito, was sufficient to kill 

 90% of juvenile 'i~iwi under experimental con- 

 ditions. The high susceptibility of this species 

 could explain its disappearance during the past 

 20 years from many midelevation forests where 

 it was previously common. 



Strategies for breaking the cycle of vector- 

 transmitted diseases include intensive environ- 

 mental management to reduce mosquito breed- 

 ing sites, chemical and biological control 

 agents, genetic manipulation of the vector pop- 

 ulation, and release of sterile male mosquitoes. 

 In addifion, removal of feral ungulates from 

 critical forest habitats may reduce available 

 breeding sites and mosquito densities to levels 

 too low to support disease transmission, but this 

 needs to be evaluated under controlled condi- 

 tions. Efforts by land managers in Hawaii to 

 fence and control feral ungulates will provide 

 an opportunity to coordinate disease research 

 with management. 



Additional Research and Management 



Conservation programs in Hawaii need to 

 have both species and ecosystem components. 



