3.5 Observations of Seabirds along a 



14,892-km Cruise Track in the Tropical 

 Pacific Ocean and the Bohol, Sulu, and 

 South China Seas 



ANGELA K. KEPLER 1 , CAMERON B. KEPLER\ DAVID H. ELLIS 5 , and JEFFREY S. HATFIELD } 

 US Fish & Wildlife Service, Patuxent Wildlife Research Center, Southeast Research Station, Athens, Georgia, USA 

 *US Fish & Wildlife Service, Patuxent Wildlife Research Center, Laurel, Maryland, USA 



Introduction 



This study forms a small part of the research efforts of the 

 First Joint US-USSR Central Pacific Expedition (Line and 

 Phoenix Groups. Gilbert Islands. Micronesia, inland Philippine 

 Seas, and South China Sea). Seabird observations were made 

 from the Soviet research vessel (R/V) Akademik Korolev 

 (7.000 tons, 1 24 m in length) from Hilo, Hawaii, to Singapore 

 (Figs. 1,2) via Christmas Island (02°N, 157°W) and Caroline 

 Atoll (10°S, 150°W). 



The primary objectives of the expedition were to 

 characterize and contrast the fundamental oceanographic, 

 hydrochemical, microbiological, hydrobiological, and 

 ecological parameters of arctic and tropical marine ecosystems. 

 Emphasis was placed on the primary productivity and ecological 

 health of these two major areas, including pollution studies 

 involving multidisciplinary experiments conducted jointly by 

 scientists of both countries. 



In this paper, we report the marine distribution of seabirds 

 and other transoceanic migrants, such as shorebirds and ducks, 

 during the tropical portion of the cruise, which covered 

 14.892 km from 9 September to 31 October 1988. Weconducted 

 a total of 1 6 1 hours of observations on transects representing an 

 area of 3,609 km 2 , during which time the ship traveled 

 4.5 1 1 km (Table 1 ). Our observations covered 21 degrees of 

 latitude and 1 07 degrees of longitude. Because the cruise track 

 traversed many island archipelagos, we subdivided it into the 

 following 7 regions (Figs. 1,2), all lying between 14°N and 

 10°S latitudes: 



Region 1 Line Islands, including waters south of Hawaii 

 (150°Wto 160°W); 



Region II Phoenix Islands to the international dateline ( 1 60°W 

 to 180°); 



Region III Gilbert Islands (180° to 165°E): 

 Region IV Caroline Islands', Micronesia ( 165°E to 136°E); 

 Region V Philippine Sea and Basin ( 1 36°E to 1 25°E); 

 Region VI Inland Philippine Seas: Bohol (Mindanao) and 

 Sulu Seas. Balabac Strait (125°E to 1 17°E); and 



Not to be confused with Caroline Atoll (Island), Southern 

 Line Islands, at 10°00S latitude, 1 50° 13'W longitude. 



Region VII South China Sea. Philippines to Singapore ( 1 1 7°E 

 to 103°E). 



We interpret our results within the contexts of 1. breeding 

 phenology, nonbreeding dispersion, and migration (Fig. 3); 



2. proximity to known breeding colonies and nearest landfalls; 



3. previous at-sea records; 4. anthropogenic factors such as 

 population density, environmental alterations to coastal habitats, 

 and pollution (see Chapters 2,3); and 5. general areas of 

 upwelling, providing locally rich feeding areas. 



Seabirds, more than any other group of living organisms, 

 illustrate that the world's oceans are united. For example, 

 parasitic jaegers (Stercorarius parasiticus) breed in Siberia 

 and Alaska, then migrate south to winter in south temperate 

 waters of the Pacific. Indian, and Atlantic Oceans. En route, in 

 the Pacific, they skirt all four continents, passing through 150 

 degrees of latitude and at least 80 degrees of longitude. 



The 1988 US-USSR expedition provided an opportunity 

 to study assemblages of birds, highly visible indicators of the 

 health of marine ecosystems, over vast areas of the Pacific 

 Ocean. Studies of the marine environments utilized by these 

 birds provide the knowledge to encourage practical action 

 toward their conservation. 



Previous Studies 



Although the broad distributions of central and western 

 Pacific seabirds are well-known (Murphy, 1936; Mayr, 1945; 

 Delacour & Mayr, 1946; Baker, 1951; Clapp, 1967; Clapp & 

 Sibley, 1967, 1968; Amerson, 1969; King, 1970. 1973, 1974a; 

 Nelson, 1975, 1978; Perry, 1980; Engbring, 1983; Garnett. 

 1983, 1984; Gould, 1983; Harrison, 1985; Pratt, Bruner & 

 Berrett, 1987), much remains to be learned of their detailed 

 distribution patterns in the Southern Line Islands and areas 

 west of Micronesia. Information on seabirds in southeast Asia, 

 at least in English, is incomplete and often outdated (Delacour 

 & Mayr, 1946; Delacour, 1947; King & Dickinson, 1975; 

 Nelson, 1978; Harrison, 1985). We are unfamiliar with the 

 literature in Asian languages and have not pursued the numerous 

 reports and publications resulting from marine oriented trips to 

 islands and reefs in the Asian region through which we passed 

 (UNEP, 1984a,b;IUCN, 1 988 a,b), some of which may contain 



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