Crested Tern ( Thalasseus hcr^ii) : We observed only two 

 of these large, coastal, yellow-billed terns. Although a resident 

 breeder on several island groups in the central and western 

 Pacific and southeast Asia, it is everywhere uncommon ( King, 

 1967; King & Dickinson. 1967; Amerson. 1969). Our birds 

 appeared on the last day of the cruise as we entered Singapore 

 Roadstead. 



Brow nor Common Noddy (Anous stolidus) : This abundant 

 tern breeds on almost all island groups in the Pacific, extending 

 westward into southeast Asia (King, 1967; Pratt el ai. 1987). 

 Although widespread, it generally occurs within 80 km of its 

 breeding colonies. Much remains to be learned of the precise 

 details of its dispersal patterns (Harrison, 1985). 



The brown noddy was the third most abundant bird seen 

 from the R/V Akademik Korolev (N = 259). An additional 

 203 noddies, seen in Micronesia, could not be identified to 

 species. Since we saw no black noddies (A. minutus) in 

 Micronesia, it is likely that they were also A. stolidus. 



Although we sighted brown noddies in the Line, Phoenix. 

 Gilbert, and Caroline Islands, we counted only five birds total. 

 All well out to sea, some were 900 km from the nearest known 

 breeding colony (ca. 7.700 birds at Phoenix Island. POBSP 

 estimate, in Garnett, 1983). 



Despite the fact that the Gilbert Islands are heavily 

 populated, brown noddy densities were highest there 

 (7.09 birds/10 km 2 ): they were the most abundant bird in the 

 region (Table 2). This species, which can nest in trees, is much 

 more tolerant of humans than most seabirds. Pacific Ocean 

 Biological Survey Program personnel also found that/4, stolidus 

 was common throughout the Gilberts up to 80 km from land 

 (November to December. 1962 and 1964). It breeds on six 

 islands in the southern Gilberts, including Abemama, near 

 which we observed 235 brown noddies on 8 October. 



In Micronesia, 18 brown noddies and 200 unidentified 

 noddies (probably A. stolidus) close to Pohnpei probably 

 originated on that island, where they are known to breed 

 (Baker. 1951). 



Brown noddies were regular members of feeding flocks, 

 contributing 5% of their numbers (15% if the unidentified 

 noddies are included) and participating in 36% of flocks 

 (Tables 5.7). Corresponding figures from King (1970) are 

 7 and \\9c. 



Black or White-capped Noddy (Anous minutus) : This 

 species, smaller and darker than the brown noddy, breeds and 

 disperses over the same range. It is more sedentary, however, 

 and feeds closer inshore. Water temperature plays an important 

 part in the pelagic distribution of both noddy species (Murphy, 

 1936): both are largely absent from cold-water upwellings. 



Despite the black noddy's widespread distribution in the 

 Pacific, we only observed six. Five were in the Line Islands 

 within a few kilometers of Christmas Island, where 

 approximately 10,000 breed (Garnett, 1983). The remaining 

 bird was in the Gilbert Islands, where A. minutus may still 

 breed. Twenty years ago there were small breeding colonies on 

 eight islands (Amerson, 1969), including Maiana, which lay 

 within 20 km of our cruise track. 



Greatest densities (0.11 birds/10 km 2 ) were within the 

 Line Islands, where breeding populations exceed 40,000 

 (Stoddart, 1976). Colonies are smaller in the Phoenix Islands, 



but it is surprising that we did not see one, as we passed within 

 80 km of Orona ( Hull ). where 1 0.000 birds have been reported 

 (King, 1973). None participated in feeding flocks. 



White or Fairy Tern (Gve/.v alba) : Tolerant of man, the 

 white tern breeds throughout the tropical Pacific. As with 

 noddies, it is most common within 80 km of its breeding 

 colonies, but may wander great distances out to sea (King, 

 1967; Pratt et ai, 1987). 



The white tern was the fourth most common bird (Fig. 4) 

 seen on the cruise (N = 146), occurring from the Line Islands 

 to the Philippines. Many sightings were of ones and twos; the 

 largest group (18) had been attracted to a large feeding flock 

 south of Pohnpei, Caroline Islands. 



At-sea densities of white terns, as for many other tropical 

 species, reflect in part their breeding phenology, especially for 

 the more remote islands. Line Islands densities were low 

 (0.05 birds/10 km 2 ) in September 1988 but much higher in 

 March to May 1990 (ICBP, 1990). Perry (1980) estimated 

 17,050 white terns in the Line Islands and noted that they 

 ranged widely and bred all year. Densities in the Phoenix 

 Islands were higher (0.31/10 km 2 ), a surprise considering that 

 the overall population (10,000 birds; Clapp, 1967) is smaller. 



White tern densities were greatest (2.01 birds/10 km 2 ) in 

 the Gilbert Islands, due in large part to 89 birds seen the day 

 before anchoring at Tarawa. In Micronesia, 36 G. alba were 

 observed south of Kosrae and Pohnpei, and one was found 

 north of Ulithi Atoll. Baker ( 1 95 1 ) implies that it is common 

 in Micronesia, especially on low islands: Ulithi is listed as a 

 breeding site. 



White terns are not listed for the Philippines (Delacour & 

 Mayr, 1946; King & Dickinson, 1975). The species evidently 

 rapidly decreases in density west of Micronesia. Our most 

 westerly sighting, an adult flying southwest at 1 1°00'N, 132°59'E 

 was approximately 480 km north-northwest of Belau, the 

 closest landfall, and on the extreme western Pacific limit of the 

 white tern's known range. This is the maximum distance that 

 we observed this species from land. 



Feeding Flocks 



A seabird feeding flock is regarded as an association of 

 five or more individuals acting as a unit (Gould, 1974b). In this 

 study we encountered both monospecific and mixed-species 

 flocks. We did not see any large associations of seabirds that 

 were not feeding flocks (i.e., flocks of direct migrants). The 

 following analysis deals with the size, abundance, composition 

 (species and family), and geographic distribution of the 

 14 feeding flocks we encountered. 



Flock Size and Abundance 



Flock sizes ranged from 8 to 420 birds, averaging 

 148 birds per flock. The total number of birds in feeding flocks 

 (N = 2,070) represented 56.5% of our bird sightings, a figure 

 comparable to the 69.5% found in 893 flocks by POBSP ( King, 

 1970). 



The smallest flock (N = 8), of seven white terns and one 

 brown noddy, occurred in the Gilbert Islands on 8 October. 

 The largest flock (3 October in the Phoenix Islands) was 

 monospecific (420 sooty terns). The second largest (N = 408) 



243 



