FAUNA OF THE ALEUTIAN ISLANDS AND ALASKA PENINSULA 183 



Bogoslof Island is noted for its sea lions and its murres. Here 

 again, although both species are present, we concluded that Pallas 

 murres were in the majority. In 1938, Scheffer estimated that 

 there were about 50,000 of these birds on Bogoslof. 



There is a notable colony, consisting of both species, on the 

 steep cliffs of Kagamil Island ; however, we could make no esti- 

 mate of the relative abundance of each. 



Chagulak and Amukta Islands also have their murre colonies, 

 and we found a small group on Seguam — all of these colonies 

 contained both species. On Chagulak, the Pallas thick-billed murre 

 again seemed to predominate. Both species nest on Kasatochi, 

 and unidentified murre colonies were seen at a distance on Koniuji. 

 We found 2 colonies on Attu and 3 colonies on Agattu. 



Other small groups nest on various cliffs, and the murre is 

 found almost everywhere throughout the Aleutian chain and 

 along the south side of Alaska Peninsula. On the north side of 

 the Peninsula, however, they do not occur as a nesting bird east 

 of Amak Island, because the low relatively flat coastal plain does 

 not afford proper nesting sites. 



At Agattu Island, on June 11, 1937, we obtained a specimen 

 of Pallas's murre that was weak, very thin, and still in winter 

 plumage. 



Ecology of the Murre 



The ecological reactions between gulls and murres have already 

 been discussed, but further attention should be given this ques- 

 tion with special reference to the murre. It is a well-known fact 

 that large gulls, in this instance L. gkiucescens, visit bird-nesting 

 colonies (such as those of murres) to feed on eggs and young. 

 When one observes this relationship in action for the first time, 

 one becomes apprehensive that the prey species will be drastically 

 reduced in numbers, or exterminated, through interference with 

 the reproducing function. However, the more one studies this 

 problem, the more one is impressed with the principle of mutual 

 racial adjustment, or balance. 



Amak Island may be cited as an example. There are the usual 

 colonies of glaucous-winged gulls adjacent to the murre cliffs, 

 together with several nesting pairs of northern bald eagles and 

 Peale's falcons. I visited this island in the summer of 1925, in 

 the month of July. There was plenty of time to take stock of the 

 avifauna of this little island, for we had to remain 9 days before 

 the weather permitted departure in the small boat. In 1936, we 

 visited the island again, which gave us the opportunity for com- 

 parison after an interval of 11 years. Conditions had obviously 



