a) 1 2 October, two in feeding flock at 04°03'N, 163°3 1 'E; 



b) 13 October, five flying north, one in feeding Hock 

 at 06°16'N, 157°51'E. Heavy squalls and winds from the 

 north: 



c) 1? October, one Hying east at 10°19'N, 147°39'E; and 



d) 25 October, six Hushed by ship from resting position on 

 water at 05°44'N. !08°01'E. 



South Polar or McCormick's Skua iCaiharacta 

 maccormicki) : This thickset, gull-like seabird breeds in 

 Antarctica. It is an uncommon migrant in the Pacific, known 

 only from the Hawaiian. Line, and Phoenix Islands, possibly 

 west to the Gilbert Islands (Pratt etui. 1987). Harrison (1985) 

 notes that juveniles disperse much further north than adults, 

 possibly following a clockwise path across the Pacific rim past 

 Japan (May-July) to British Columbia and California 

 (September-October), then back to Antarctica to breed in the 

 austral summer. 



We observed five south polar skuas (three light- and one 

 dark-phased adults and one juvenile) in Regions III and IV 

 (Gilbert and Caroline Islands). All Hew very close to the ship, 

 and four participated in feeding flocks. 



Our sightings fall within the known range of this species 

 ( Harrison, 1 985 ), although other authorities indicate that south 

 polar skuas do not range this far west (Mayr. 1945: Baker. 

 1951; Pratt. 1987). Since published records are sparse (they 

 were not listed in Baker. 195 1 ). our exact sightings follow: 



a) one juvenile, 8 October, flying south at OTOO'N, 

 172°40'E, just south of Tarawa, Gilbert Islands. 



b) two adults, light phase, 12 October, in a feeding flock 

 at 04°03'N, 1 63°3 1 'E, south of Kosrae. The feeding flock was 

 composed of six species: two south polar skuas, two Pomarine/ 

 parasitic jaegers. >200 sooty terns. 17 wedge-tailed shearwaters 

 (dark phase). 1 Kermadec petrel. 2Bulwer'spetrels. Itdeveloped 

 in midmorning immediately after a series of rain squalls had 

 moved through the area from the south. 



c) two adults (one very dark, one light), 13 October at 

 05°43'N, l5°25'E,just south of Pohnpei. The dark morph was 

 flying southeast, the light one had joined a small feeding flock 

 of 22 wedge-tailed shearwaters. Four hours later heavy winds 

 and squalls hit us from the north, after which a massive 

 concentration of fish attracted a large feeding flock which 

 included an unidentified skua. 



The highest densities of south polar skuas were in 

 Micronesia (0.05 birds/10 km : ). 



Pomarine Jaeger or Pomarine Skua {Stercoruriits 

 poinariimsY . This Holarctic-breeding jaeger migrates south to 

 winter throughout the tropical, subtropical, and temperate 

 areas of the Pacific. Evidently in good breeding years adults 

 move south in August-September, followed by juveniles in 

 September-October (Harrison, 1985). Our entire cruise track 

 was within its known range. 



From 22 to 25 October we observed three Pomarine 

 jaegers in the Sulu Sea and South China Sea ( Table 4 ). One was 

 a light-phase adult, the rest, juveniles. One juvenile was 

 flushed from a resting position on the water, while the others 

 flew east or south. The highest densities of this species were 

 in the South China Sea (0.07 birds/ 10 km 2 ). 



Parasitic Jaeger or Arctic Skud(Stercorarius parasiticus) : 

 The Holarctic breeding and Pacific wintering ranges overlap 

 those of the Pomarine Jaeger (Harrison. 1985). Since this 

 species has not been recorded from the central Pacific and is 

 uncommon in the western Pacific (for example Bismarck 

 Archipelago and Bonin Islands), its migration routes are thought 

 to remain close to the continental coasts (King, 1967). King& 

 Dickinson ( 1975) mentioned that it might occur in southeast 

 Asia. 



Our observations came from the Caroline Islands and 

 South China Sea. One juvenile was sighted on 12 October, 

 south of Kosrae (04°22'N, 162°2 1 'E) flying east; and one adult 

 was seen on 14 October north of the Hall Islands (09°46'N, 

 154°43E), flying southeast. We also saw parasitic jaegers on 

 24 October off the north coast of Borneo (04°40'N, 1 13°20'E. 

 one juvenile, flying southeast) and on 25 October in the central 

 South China Sea (05°49'N, 107°30E, one adult dark morph. 

 flying southwest). 



Three of our five birds on transect were headed in a 

 southerly direction, which is appropriate for October, when 

 they dispersed south from their breeding grounds. 

 Greatest densities (Table 2) were in the South China Sea 

 (0.09 birds/ 10 knr). which fits the hypothesis that migratory 

 routes tend to follow continental coasts. 



An additional parasitic jaeger was encountered during our 

 3-day layover near Mui Bai Bung Cape, Vietnam at 05°47'N, 

 107°45'E): On 27 October at 1605 ha juvenile, dark morph 

 parasitic jaeger pursued an adult male shikra (Accipiterbadius) 

 with prey, a barn swallow (Hirundo rustica), for about 

 4 minutes (Ellis et ai, 1990). Finally the jaeger bound to the 

 shikra and/or its prey. All three birds whirled about three 

 revolutions and fell into the sea. After about 7 seconds in the 

 water, the shikra flapped away. The jaeger remained in the 

 water with its prize, drifting near the ship's stern. 

 Oceanographers later found the swallow's head in a plankton 

 net. 



Family Laridae 



This family was represented by 9 species of terns, plus 

 4 unidentified larids. totaling 2.953 individuals. Larids 

 accounted for 81% of all birds sighted on the cruise. They 

 dominated the pelagic waters of Regions I to IV, after which 

 their numbers diminished considerably. Sooty terns (Sterna 

 fuscata) were the most abundant species overall, accounting 

 for 62.8% of all birds seen on the cruise (Fig. 3), with a 

 maximum density of 43.27/10 knr in the Phoenix Islands. 



Larids. which characteristically breed on oceanic islands 

 (sooty tern, black and brown noddies, white tern), were present 

 in far greater abundance than species that typically inhabit 

 areas closer to continents (Caspian tern, S. caspia; black-naped 

 tern, S. sumatrana; and bridled tern, 5. anaethetus). We 

 expected to see far more coastal birds in southeast Asia. 

 Human population pressures and habitat alteration evidently 

 weigh heavily on the natural resources in this area. 



Sooty, white, and noddy terns were major participants in 

 feeding flocks, accounting for 88.129! of all Hocking birds 

 (Table 5). 



241 



