Fig. 3. Status ol bud species observed along the cruise track of the R/V 

 Akademik Korolev, 15 September— 3 1 October 1988. Nonbreeding 

 visitors and migrants migrate north or south to breed. 



tropicbirds, and white terns (Gygis alba). These different 

 detection distances were used as a basis for calculating the 

 densities and area coverages for each different species (Hunt 

 era/., 1 98 I;Briggs <■/<//.. 19871. Forease of comparison within 

 regions and with previous studies (King, 1970; Tasker et ai, 

 1984) and because the number of birds normally seen in 

 tropical seas is lower than that observed in colder waters, bird 

 densities were calculated in 3 ways: number/hour (per 

 2 observers), number/10 linear km, and number/10 km 2 . In this 

 paper, numbers/ 10 km' are used for comparison between 

 species and regions; the other 2 calculated values are reported 

 in Table 2. 



Prior to the expedition, we examined skins of Pacific 

 seabndsat the US National Museum. Washington. DC. focusing 

 on variable, polymorphic, and particularly difficult species to 

 identify. Terminology used in this paper follows the American 

 Ornithologists' Union Check-list (AOU. 1983. 1985). The 

 order of species within families, and alternate English names, 

 follow Harrison ( 1985). 



Results 



Forty-six species (or field-recognizable subspecies) were 

 observed along the 14.892-km cruise track of the R/V Akademik 

 Korolev from 15 September to 31 October 1988 (Figs. 1,2). 

 These were represented by members ol 1 I families of seabirds 

 (including gulls, terns, and skuas), shorebirds (including 

 phalaropes), and ducks (Table 3). 



The most abundant species was the sooty tern {Sterna 

 fusi ata), accounting for 62.8', of the total number of birds 

 (Fig. 3), but restricted to Regions I through IV. Noddy tern 

 {Anous sp.. primaril) brown noddy, A vtolidus), wedge-tailed 

 shearwatei I Puffinus pacificus), and white tern followed as the 

 next most frequently observed species We observed birds 

 belonging to the following three broad groupings (Fig. 3. 

 fable 4 ); 



a) Resident breeders . Seabirds may or may not have 

 annual breeding cycles, which affects the temporal patterns of 

 their dispersion at-sea. Within an archipelago, a species may 

 exhibit asynchronous egg-laying periods on different islands 

 or in separate colonies on the same island. For example, in the 

 Line Islands, red-footed boobies (Sahi sulci) laid primaril) 



TABLE 2 



Seabtrd densities along the cruise track of the R/V Akademik 

 Korolev, 15 September-31 October 1988. 



Region 



Species 



Number Birds 

 Per Hour Peril) Per 



Linear Km 10 Km 3 



Phoenix petrel 

 Tahiti/Phoenix petrel 

 Herald petrel 

 White-necked petrel 

 Cook's petrel 

 Stejneger's petrel 

 Bulwer's petrel 

 Unidentified petrel 

 Flesh-footed shearwater 

 Wedge-tailed shearwater 

 Sooty shearwatei 

 Christmas shearwater 

 Audubon's shearw ater 

 Unidentified shearwater 

 Unidentified shearwater/ 



petrel 

 Wilson's/Madeiran 



storm-petrel 

 Leach's storm-petrel 

 Unidentified storm-petrel 

 Red-tailed tropicbird 

 Masked booby 

 Red-footed booby 

 Brown hoohy 

 Great frigatebird 

 Bristle-thighed curlew 

 Gray-backed tern 

 Soot) tern 

 Brown noddv 

 Black noddv 



White tern 

 Unidentified tern 



Phoenix petrel 

 Mottled petrel 

 Herald petrel 

 While necked petrel 

 Cook's petrel 

 Bulwer's petrel 

 Unidentified petrel 

 Flesh-footed shearwater 

 Short i.uled shearwatei 

 Wedge tailed shearwater 

 Soot) shearwater 

 Christmas shearwatei 

 Little shearwatei 



0.17 

 0.03 

 0.07 

 0.10 

 0.20 

 0.06 

 0.10 

 0. 1 7 

 0.03 

 1.37 

 0.50 

 0. 1 3 

 0.17 

 0.10 

 0.70 



0.37 



0.07 

 0.01 

 0.03 

 0.04 

 0.08 

 0.02 

 0.04 

 0.07 

 0.01 

 0.53 

 0.19 

 0.05 

 0.07 

 0.04 

 0.03 



0.14 



0.1 1 



0.03 



0.04 

 0.07 

 0.13 

 0.06 

 0.20 

 0.11 

 0.03 

 0.88 

 0.32 

 0.09 

 0.11 

 0.07 

 0.04 



0.72 



228 



