Avifauna of Enewetak Atoll 



Chapter 1 3 



ANDREW J. BERGER 



Professor Emeritus. Department of Zoology 

 Uniuersiti/ of Hawaii 

 Honolulu. Hawaii 96822 



INTRODUCTION 



Birds constitute an important element of the Enewetak 

 fauna. They form a significant portion of the biomass of 

 larger land animals, and they also arc important foragers 

 of the surrounding ocean, particularly of the shallow reef 

 areas. The isolation of Enewetak— 200 km from the 

 nearest other land— dictates that the birds that have 

 arrived there have had to be strong fliers; this is especially 

 true for migrant spwcies. 



At least 41 species of birds have been recorded at 

 Enewetak Atoll. Amerson (1969, and included in the EIS 

 of 1974) listed 32 species; Johnson and Kienholz (1975) 

 added three; Temme (1979) and Hailman (1979) added six 

 more. A checklist is included as Table 1. These birds are 

 described and illustrated by King (1967). Earlier papers 

 dealing with the avifauna of Enewetak were those of Gleize 

 and Genclly (1945), Woodbury (1962), Pearson and Knud- 

 sen (1967), and Carpenter et al. (1968). 



No endemic species and no passerine species inhabit 

 the low islets of Enewetak. The islets presumably are too 

 low, too small, and too remote from major land masses to 

 have been colonized by birds that could have evolved into 

 endemic forms (Berger, 1979). Many of the native seabirds 

 are species that have a vast range in the Pacific region, 

 and many of them spend only the breeding season on land. 

 Of interest is the migration of the long-tailed cuckoo 

 (Eudi/namis taitensis) from New Zealand to the winter 

 range on Enewetak and other islands from the Bismarck 

 Archipelago eastward to the Marquesas Islands. 



The bird fauna of Enewetak, however, is not well- 

 known, primarily because few observers have been able to 

 spend extensive periods of time on the various islets. Any 

 significant effort over a period of time would certainly add 

 other species to the list. For example, David Anderson 

 (unpublished), a former Peace Corps volunteer residing on 

 Ujelang Atoll, recorded 36 species of birds from that atoll 

 between June 1975 and February 1977; a number of 

 these species have not yet been recorded at Enewetak. 



At least 12 species are known to breed on the atoll, 

 and at least four others are thought to nest there. Many 

 other birds probably include Enewetak within their range. 

 Owen (1977), King (1967), and Baker (1951) list a number 

 of species known from the Marshall Islands and other adja- 

 cent areas that have not yet been recorded at Enewetak. 

 The Marshallese names for the birds of Enewetak have 

 been listed by Goo and Banner (1963). 



The importance of predators other than man on birds 

 at Enewetak is not well-known. Amerson (1969) suggested 

 that both the coconut crab (Birgus latro) and Coenobita 

 rugosa eat eggs and young birds. Reese (personal 

 communication) observed a coconut crab catch a white 

 tern by the wing and drag it into the crab's burrow under 

 coconut debris at the base of a coconut tree. The tern 

 apparently had been frightened from its perch by Reese's 

 night survey team. Certainly, land crabs are scavengers 

 and feed on bird carcasses when they are available. 



On Igurin Island, however, Helfman (1973) did not see 

 coconut crabs feeding on either birds' eggs or young birds. 

 He noted that coconut husk and meat, plus a variety of 

 other items, were eaten. Igurin has large numbers of birds, 

 and if they were common prey of coconut crabs, this 

 almost certainly would have been observed. Amerson 

 (1969) and Berger (1981) report that both Rattus rattus 

 and R. exulans eat bird eggs and young. Medina and Jack- 

 son (MS) found no evidence for this, but Temme (1982) 

 reported that rats may have preyed on the eggs of Sterna 

 fuscata on Aomon. The monitor lizard, Varanus indicus, is 

 known to prey on birds and their eggs (Amerson, 1969), 

 but because it is virtually certain that the population previ- 

 ously present on Japtan no longer exists, this potential 

 predator is now gone. The return of the Marshallese popu- 

 lation to Enewetak again makes man the major predator 

 on birds at Enewetak. 



Until the recent return of the Marshallese population to 

 Enewetak, the major effect of man on the birds had been 

 the alteration of the habitat by the fighting during World 

 War II and the subsequent testing activifles. The bird 

 population of Enewetak certainly suffered during the battle 

 in 1944 and thereafter when the atoll served as a staging 

 area for campaigns farther to the west. The coconut palms 

 and other vegetation were destroyed, and construction of 

 the airfield and support facilities drastically reduced the 



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