c) Direct migrants . This grouping includes shorebirds 

 ( plovers, sandpipers, phalaropes ) and ducks as well as seabirds. 

 They nunc quickly through tropical waters from wintering 

 grounds further north or south en route to breeding areas in the 

 opposite hemisphere. Although some follow general routes 

 and can be predicted at certain times of year, the overall dearth 

 of studies in certain portions of the Pacific leaves much to be 

 learned of their at-sea distribution. For example, Stejneger's 

 petrel (P. longirostris) migrates from Chile to Japan, yet 

 sightings had been scant in between before this expedition. 



Species Accounts 



Family Procellariidae 



Shearwaters and petrels provided the greatest species 

 diversity (17) of any family. Seven breed and disperse within 

 the tropical Pacific, 1 1 breed in the temperate South Pacific and 

 migrate to wintering grounds in the North Pacific, and 1 breeds 

 in the temperate North Pacific and migrates south to winter 

 (Table 4). 



Although we did not encounter large migrating flocks, this 

 family ranked second in total numbers seen (447; Table 3) and 

 was particularly abundant in Regions I and II (Line and 

 Phoenix Islands), after which species richness declined markedly 

 to the west (Table 4). The western limit of procellariids 

 (wedge-tailed shearwaters) was the Sulu Sea (08°47'N, 

 121 28'E). 



Densities of individual species ranged from the rarer 

 migrants at 0.03 birds/10 km 2 (Table 2) to the widespread 

 resilient breeder, wedge-tailed shearwater, whose numbers 

 peaked in the Line Islands at 0.88 birds/ 1 km 2 . Several species 

 contributed to feeding flocks (Table 5 ). accounting for 10% of 

 their participants. 



Phoenix Petrel (Pterodroma alba) : All seven of this 

 rather uncommon species were sighted in Regions II and III. 

 within its relatively small range in the central Pacific. Phoenix 

 petrels sighted in the Line Islands were either within 1 .200 km 

 of their breeding grounds at Christmas Island or flying west 

 toward colonies in the Phoenix Islands. Their highest densities 

 were in the Line Islands (0.1 1/10 km 2 ). None associated with 

 other birds or participated in feeding flocks. 



Tahiti/Phoenix Petrel (Pterodroma roM rata or alba) : One 

 Pterodroma found slightly east of Maiden Island (central Line 

 Islands i was either a Tahiti or a Phoenix petrel, look-alikes 

 difficull to distinguish in the field. Tahiti petrels breed in the 

 Society and Marquesas Islands. 800 km and 1.670 km. 

 respectively, from its observed position. 



Mottled Petrel (Pterodroma inexpcciata) : A single bird 

 was seen flying southeast near Birnie Island (Phoenix Group) 

 on 4 October. This species breeds in New Zealand during the 

 austral summer, so this individual was likely migrating south 

 from its winter quarters in the North Pacific. Its density in 

 Region II was 0.03/10 km 



Kermadec Petrel (Plerodroma ne v lee la) : The Kermadec 

 petrel breeds in several island groups just south of the Tropic 

 ol Capricorn from Lord Howe Island to the coast of Chile. 

 Formerly considered sedentary, recent records indicate thai it 

 ranges widely into the North Pacific (Gould iV' King. 1967: 



Amerson, 1969; Harrison. 1985; Bailey et al., 1989). Several 

 records exist for the area extending from just south of Hawaii 

 to the Marshall and Phoenix Groups. An old record from Duke- 

 of-York Island (Bismarck Archipelago) indicates that this 

 species may also occasionally straggle almost to New Guinea 

 (King, 1970). 



Kermadec petrels are not listed for the Gilbert Islands 

 (Amerson, 1969) nor for any of the Caroline Islands (Pratt 

 et al.. 1987): hence, the following observations extend the 

 known range for this species: 2 Kermadec petrels ( 1 light and 

 1 dark phase) were seen on the morning of 1 2 October at the far 

 eastern edge of Micronesia (04°03'N. 163°30'E). approximately 

 157 km south of Kosrae. The dark-phase petrel was flying 

 directly south, while the light-phase bird had joined a feeding 

 (lock of over 200 sooty terns mingled with small numbers of 

 wedge-tailed shearwaters. Bulwer's petrels anil south polar 

 skuas (Catharacta maccormicki). Kermadec petrels were seen 

 only in Region IV with a density of 0.03/10 km 2 . 



Herald Petrel (Plerodroma arminioniana) : The Pacific- 

 breeding range of this medium-sized gadfly petrel includes 

 Easter Island, the Pitcairn Islands, Tuamotus. Marquesas. 

 Gambiers, and, further west. Tonga and Chesterfield (Coral 

 Sea). In the nonbreeding season, herald petrels remain primarily 

 in the Southern Hemisphere, occasionally wandering north of 

 the equator (Harrison. 1985; Bailey etal.. 1989 (where they are 

 typically observed more than 150 km from land (King. 1970). 

 We observed four adults (three dark phase, one light) in the 

 Line, Phoenix, and Gilbert Groups. Two occurred just outside, 

 the others within, the known pelagic range of this species 

 (Harrison. 1985). The two dark-phase birds, beyond the 

 eastern borders of their known range (05°24'N. 156 o 60'W), 

 were flying southwest on 2 October (ca. 380 km east of 

 Washington Island. Line Group). Densities were highest in the 

 Line Islands (0.04/10 km 2 ). Three of the birds were Hying 

 directly southwest. 



White-necked Petrel ( Pterodroma externa) ( includes both 

 P. e. externa and P. e. cervicalis): We observed 10 of these 

 gadfly petrels: 3 occurred in September and October within 

 their main wintering grounds in the central Pacific between the 

 equator and Hawaii (0.07/10 km 2 ), and 7 spanned the Phoenix 

 Group, where densities were highest (0. 1 7/10 km 2 ). They are 

 known to be abundanl in (he former location from May to 

 November ( King. 1 967 ). 



There are two subspecies that breed on opposite sides of 

 the temperate Pacific; the white-necked {externa) in the 

 Kermadec Islands northeast of New Zealand, and the Juan 

 Fernandez (cervicalis) in the Juan Fernandez Islands of Chile. 

 Seven birds were flv ing south or southwest I four Hew together), 

 presumably returning to breed on southern temperate islands 

 during the austral summer. 



Cook's Petrel (Pterodroma cooki) : Cook's petrel breeds 

 m the austral summer in New Zealand and the Juan Fernandez 

 Islands. Although this iransequatonal migrant ranges widelj 

 between the south and north temperate Pacific as tar as the 

 Aleutian Islands, its pelagic movements are not fully understood, 

 lew records exist from the central Pacific. There are two 

 records from the Phoenix Islands and sightings near the Hawaiian 

 Islands in (he northern spring (King, 1967; Harrison. 1985: 



232 



