Dark-phase birds accounted for 979? of sightings where 

 color phase was noted (57). Only two light-phase individuals 

 were seen (Region 1. 10°46'N and ()6°45'N), both south of 

 Hawaii, where the majority of the population is light phased. 



Short-tailed Shearwater {Puffinus tenuimstris) : A wide- 

 ranging transequatorial migrant, with movements and breeding 

 phenology similar to those of the flesh-footed and sooty 

 shearwaters (P. griseus), this species breeds off southeastern 

 Australia and winters off the west coast of North America and 

 the Bering Sea. We observed one adult (2 October) heading 

 south through the eastern extremity of its known migratory 

 pathway, the eastern Phoenix Islands (06°29'S, 162°19'W). 



Sooty Shearwater (Puffinus griseus) : Sooty shearwaters 

 arc wide-ranging, transequatorial migrants that breed from 

 October to May in the Southern Hemisphere on islands off 

 Australia. New Zealand, and Chile, migrating to equivalent 

 high latitudes in the northern Pacific during the nonbreeding 

 season. We observed very small numbers of birds on their 

 annual southward migration. All 17 observations were in the 

 south-central Pacific. We saw them on only 2 days: 

 16 September (N = 15). east of Washington Island (Line 

 Group) and 2 October (N = 2), between Sydney and Starbuck 

 Islands (east of the Phoenix Group). All were adults 

 Hying south, and none were feeding or associated with other 

 species. Densities were 0.32 birds/ 10 km : in Region I and 

 0.05 birds/10 km 2 in Region II. Enormous flocks of migrants 

 have been encountered in this area ( King, 1 967: CBK. personal 

 observation). 



Christmas Shearwater (Puffinus ncitivitatis) : The Christmas 

 shearwater, a year-round resident in the tropical Pacific, tends 

 to remain fairly close to its breeding grounds all year, although 

 it is generally seen more than 180 km from land (King. 1970). 

 We observed four individuals in the Line Islands (05°N, 

 157°W) that were Hying west, and a single bird in the Phoenix 

 Group, flying north. Densities were low: 0.09 birds/10 km 2 

 (Line Islands) and 0.03 birds/10 km 2 (Phoenix Islands). 



Little Shearwater (Puffinus assiniilis) : This small, 

 distinctive "aukish" shearwater breeds and disperses within 

 south temperate waters, generally only occurring at-sea north 

 to 25°S latitude. However, its pelagic dispersal is not well 

 known and wanderers have been recorded near the Marquesas, 

 Marshall, and Hawaiian Islands (King. 1967). Clapp ( 1967) 

 listed a doubtful record from Christmas Island in the late 

 I950's. We add a single straggler, seen on 4 October in the 

 Phoenix Islands (03 59'S, 171°31'W) close to Birnie Island 

 and Hying north. Within 20 minutes, we also observed the 

 similar Audubon's shearwater: both flew close to the ship, 

 enabling us to compare si/e, bill length, and the degree of white 

 present on the underw ings. 



Audubon's Shearwater (Puffinus Ihcnninicri) : This small 

 shearwater is resident in the central and western Pacific: our 

 five sightings ( Regions I and II ) were within its known range. 



Our sightings of Audubon's shearwater at 02°N. 157 W 

 were evidently from adjacent colonies on Christmas Island. 

 However, we saw two birds flying northwest in the Southern 

 I ine Islands (06 32'S, I52°35'W) on 21 September 1988, 

 approximately 1. 1 00 km from Christmas Island and more than 

 1,800 km from Phoenix Island, the nearest known colonics 



(Clapp. 1967; Stoddart. 1976: Garnett. 1983). Since this 

 species usually ranges at sea within 180 km of its breeding 

 islands (King. 1967). we speculate that an unknown colony lies 

 w ithin the Southern Line Islands. Maiden Island, approximately 

 400 km distant from the Audubon's shearwaters in question, is 

 a likely possibility. Little visited by biologists, approximately 

 one-third of its interior is covered by a landlocked, supersaline 

 lagoon with subterranean connections to the sea, containing a 

 maze of interconnected islets and salt flats (Garnett. 1983; 

 RNZAF. 1986). These islets have never been surveyed by 

 ornithologists (R.B. Clapp. personal communication). They 

 provide potential habitat for Audubon's shearwaters, since 

 they resemble sites occupied by this species on Christmas 

 Island. Bloxham ( 1925) recorded two species of shearwaters 

 of unknown identity on Maiden: Garnett ( 1983) proposes that 

 one of them may have been Audubon's shearwater. Starbuck. 

 another stark, arid guano island with a similar interior, is 

 another probable source. 



On 5 May 1990. a single Audubon's shearwater was 

 observed flying north-northwest around 10°S, 155°W, 

 approximately 640 km due south of Maiden (ICBP. 1990). 

 further suggesting the presence of a colony in the Southern 

 Line Islands. 



In Region II, we saw one Audubon's shearwater in a 

 feeding flock at 03 D 57'S. 171°31'W. near a large breeding 

 colony (ca. 12.000 birds) on Phoenix Island (Garnett. 1983). 



Family Hydrobatidae 



The storm-petrels were represented by three (possibly 

 four) species (Table 4) and five unidentified individuals. 

 Small numbers (N = 26) were present at sea from the Line 

 Islands west to Micronesia. Wilson' s/Madeiran storm-petrel 

 in the Line Islands accounted for the greatest densities 

 (0.72 birds/ 10km : ). Overall, storm-petrels accounted for().7'< 

 of the total number of birds on the cruise (Fig. 4). Typically 

 solitary feeders, they never participated in feeding flocks. Our 

 westernmost observation was of a Wilson' s/Madeiran storm- 

 petrel at 03°59'N, 163°45'E (south of Kosrae). 



Wilson' sSiorm-PelvcliOcecinitesoceiiniats) and Madeiran 

 (Harcourt's) Storm-Petrel (Oceanodronui custro) : Wilson's 

 storm-petrel breeds on subantarctic islands off South America 

 and in Antarctica and ranges widely throughout all the world's 

 oceans (Murphy. 1936: Murphy & Snyder. 1952). In the 

 Pacific it migrates northward to wintering grounds within 

 tropical and north temperate waters (Harrison. 1985). It is 

 rarely seen in the Pacific except in the far east (King. 1967; 

 Huber. 1971;Crossin, 1974). Records and sightings exist from 

 the Marshall Islands. Solomons. New Hebrides. New Caledonia, 

 waters close to Hawaii, the Phoenix Islands, and Christmas 

 Island. 



The Madeiran storm-petrel, although not congeneric with 

 Wilson's, appears remarkably similar in the field. It is a 

 resident breeder in the tropical Pacific: therefore, its dispersal 

 range overlaps with the wintering areas of Wilson's, primarily 

 west of the international date line. 



Eleven Wilson/Madeiran storm-petrels were observed at 

 00°28'S, 156°32'W, east of Jarvis Island. Hying southeast. A 

 Wilson's, flying south, was located southeast of Kosrae 



236 



