Cape Thompson. In 1960, 118,000 pairs of 

 Thick-billed and 78,500 pairs of Common 

 Murres were breeding on the cliffs. Summer 

 observers have found them primarily in the 

 waters around breeding cliffs. Swartz (1967) 

 reported that during the breeding season U. 

 lomvia constituted 90 percent of all murres 

 seen further than 5 miles from shore. Since 

 60 percent of the murres breeding on the cliffs 

 are U. lomvia, he believed that U. aalge fed 

 closer to shore at least during the breeding 

 season. He reported few murres feeding more 

 than 40 miles from the cliffs. The Thick-billed 

 Murre winters in open water at the edge of 

 the pack ice and moves north and south with 

 the ice margin. There is thus no well-defined 

 migration, and birds have been recorded as far 

 north as Barrow in December. 



We made scattered sightings of single birds 

 in the eastern section of the study area, but 

 only on the most westerly transects were mur- 

 res observed in numbers (fig. 29). They could 

 not be identified to species, however, and the 

 similarity of murres and the Horned Puffin at 

 a distance caused us to list some birds as large 

 black and white alcids (fig. 30). Murres were 

 seen throughout the day on 18 October in the 

 Bering Strait (fig. 28). Murres feed by diving 

 for fish and crustaceans. The stomach of the 

 one Common Murre collected (table II) con- 

 tained remains of Arctic Cod and a single 

 larval hermit crab (Pagtiriis spp.) (table V) . 



Guillemots (Cepphus spp.) 



Both Black (Cepphus grijlle.) and Pigeon 

 Guillemots (C. columba) breed in the Chukchi 

 Sea. The Black Guillemot is also found in the 

 North Atlantic and Arctic Oceans, but the 

 Pigeon is restricted to the Pacific sector. The 

 Chukchi is the only area where the two species 

 are sympatric, with both breeding on Herald 

 and Wrangel Islands and at Cape Thompson. 

 The Pigeon Guillemot also nests in the Bering 

 Strait area while the Black Guillemot is 

 suspected to nest near the Seahorse Islands 

 (Bailey, 1948). Black Guillemots have recently 

 taken advantage of artificial "burrows" pro- 

 vided by discarded oil drums and have nested 

 at the tip of Point Barrow (MacLean and 

 Verbeek 1968). Swartz (1966) found fewer 

 than eight pairs of either species breeding at 

 Cape Thompson but guillemots rarely breed 



anywhere in dense concentrations. They are 

 found primarily in the littoral zone during the 

 breeding season and are generally found in 

 pelagic situations only at the edge of the pack 

 ice in the nonbreeding season. 



Some Black guillemots probably remain in 

 the Chukchi all winter, for specimens have 

 been taken in almost every month in arctic 

 Alaska and they are present whenever there is 

 open water at the ice edge. Bailey (1948) sug- 

 gests they may even live in pressure ridges 

 under the ice. 



Summer observers in the Chukchi give con- 

 flicting reports on the status of these two 

 sibling species that are not easy to separate 

 even in the breeding season. Nelson (1883) 

 observed both species and considered the 

 Pigeon Guillemot to be the more common of 

 the two. He found it to be the most abundant 

 bird at Herald Island where, however, he also 

 observed numerous Black Guillemots. Jacques 

 (1930) did not observe the Pigeon Guillemot 

 north of the Diomedes but found the Black 

 Guillemot common north of 69° N. He found 

 it to be especially abundant at Herald Island 

 and at the edge of the ice. In the eastern 

 Chukchi, Swartz (1967) reported only the 

 Pigeon Guillemot. One of two sightings was 

 off Cape Li.sburne and the other at the edge of 

 the pack ice at 70^50' N, leS-^SO'W. 



All guillemots we observed were in winter 

 dress and were identified as C. grylle (figs. 26 

 and 32). The only possible sighting of C. 

 cohnnba was an immature individual west of 

 Cape Lisburne. Although it was not common 

 at Barrow, a flock of 30 individuals was ob- 

 served in that area. Lesser numbers were seen 

 on transects 4-8 from Barrow to the study 

 area. In the study area, the great majority of 

 observations were on the most northerly tran- 

 sects near the edge of the pack ice with the 

 largest concentrations in the eastern portion 

 of the study area. None was seen in the Bering 

 Strait. 



Fish are the primary food of guillemots, but 

 crustaceans sometimes also constitute a large 

 portion of the diet. The stomachs of the three 

 Black Guillemot specimens collected (one adult, 

 two immature; table II) all contained remnants 

 of Arctic Cod (table V). One also contained 

 four crustaceans: two Gammaracanthus lor- 



121 



