.?7S 



Hawaii — Our Liriiii; Rcsiiuires 



Table 2. Continued. 



^Islands: All — all ma|or Hawaiian Islands; Ha — Hawaii; Ka — Kauai; La — Lanai; Ma — Maui; Mo — Molokai; NW — Northwest Hawaiian Islands; Oa 



— Oahu, species extinct where island listed in parentheses. 



"Listing status C — candidate for listing; E — endangered; EX — extinct, T — threatened species 



"^Population and trend data source; 1 - Scott et at (1986); 2 - Harrison (1990); 3 - Ellis et al (1992), 4 - Engilis and Pratt (1993); 5 -recent survey 



data (J Jacobi, unpublished data) 



<*Trend D — declining, EX' — possibly extinct; I — increasing; S — stable; Unk — unknown. 



elevation, where less than 10% of the native 

 vegetation remains. In addition to direct clear- 

 ing, all remaining native plant communities are 

 further degraded by disturbance and competi- 

 tion from introduced plants and animals. 



The current ranges of most Hawaiian forest 

 birds appear closely tied to the distribution of 

 forests dominated by native tree species. It is 

 unclear whether this association is due to feed- 

 ing specialization on native plants, or if other 

 factors, such as disease or predators, restrict 

 native birds from disturbed habitats. The only 

 real exception to this is the Oahu amal^ihi 

 (Hemigmitlnis virens chloris). which recently 

 appears to be colonizing habitats dominated by 

 introduced plant species around Honolulu. 



Avian Disease 



The accidental introduction of Ciilex mos- 

 quitoes in the early 19th century, and the impor- 

 tation and widespread release of domestic fowl, 

 gamebirds, and cage birds with their accompa- 

 nying diseases, are believed responsible for the 

 establishment of avian pox virus and malaria 

 {Plasmodium reliction) in Hawaiian forest bird 

 populations (Warner 1968: van Riper et al. 

 1986). The concurrent fragmentation of native 

 forests probably hastened the spread of mosqui- 

 toes and exotic birds into forest habitats, expos- 

 ing native birds to avian pox (Perkins 1893; 

 Henshaw 1902) and malaria. 



Warner (1968) first identified pox and 

 malaria as major pathogens of native forest 



birds. Van Riper et al. (1986) demonstrated that 

 the highest incidence of malaria occurs in wet 

 midelevation forests (between 900 m [3,000 ft] 

 and 1.500 m [5,000 ft]) where populations of 

 0//('.v mosquitoes overlap with highly suscepti- 

 ble native birds. Current investigations support 

 these observations. Surveys for other disease 

 agents identified a number of potentially patho- 

 genic parasites and bacteria, but none has been 

 implicated as a significant cause of mortality 

 (van Riper and van Riper 1985). 



Introduced Predators 



While introduced rats (Raltiis spp.), cats 

 (Felis catus), dogs (Canis familiaris), and mon- 

 gooses (Herpestes aiiropuuctatiis) have serious- 

 ly affected nesting waterbirds, less information 

 exists on the significance of these predators in 

 restricting the distribution and abundance of 

 upland forest birds in Hawaii (Atkinson 1977; 

 Griffin et al. 1989). Several projects have begun 

 in Hawaii to develop adequate control strategies 

 for introduced predators and to monitor the 

 response of forest bird populations to the reduc- 

 tion or elimination of these predators. 



Competition and Food 



Competition for nesting and food resources 

 by introduced birds and food resource limita- 

 tion by introduced arthropods (e.g., ants or 

 wasps) are the two most difficult of the limiting 

 factors hypotheses to evaluate. Although a study 



