LIFE HISTORIES OF NOETH AMERICAN DIVING BIEDS. 197 



in summer, we found the murres very useful in helping us to locate 

 certain islands which they frequent as breeding grounds; murres 

 are constantly flying to and from such islands in their search for 

 feeding grounds, and their unerring sense of direction leads them 

 with certainty through the densest fog. Twice we passed near the 

 dangerous volcanic rocks of Bogoslof and could not have located it 

 except by noting the direction in which the murres were flying. They 

 must fly long distances for food, for anywhere within a hundred 

 miles of their breeding resorts they were frequently in sight. 



Spring.— The Pallas's murres arrive on their breeding grounds 

 in Bering Sea early in the season, following the leads in the ice, 

 as -it breaks up in the spring, and reaching their northern summer 

 homes in the vicinity of Bering Strait before the end of May. They 

 do not begin to lay before the middle of June, and fresh eggs may 

 be found all through July or even into August. 



Nesting. — The largest breeding colony of Pallas's murres, probably 

 the largest breeding colony of any kind, that I have ever seen was 

 on the most famous volcanic island of Bering Sea, Bogoslof Island, 

 about 70 miles northwest of Unalaska. Considering the wonderful 

 volcanic performances of this interesting island, it is surprising that 

 the murres still resort to it as a breeding ground, for at each of its 

 frequent eruptions many thousands of these poor birds have been 

 killed; but still the "foolish guillemots," as they have well been 

 called, return to it again the next season. The violent eruptions of 

 the summer of 1910 threw up enough material to join together the 

 three little islands forming the Bogoslof group. In 1911 the vol- 

 cano had subsided and the towering peaks of Castle Eock, from 200 

 to 300 feet high, were literally covered with nesting murres. I could 

 hardly hazard a guess as to how many hundred thousand murres 

 were breeding on this and on other portions of the island. On the 

 steep sides of the rocky peaks every available ledge, shelf, or cavity 

 was occupied by murres, sitting as close as they could, in long rows 

 on the narrow ledges and in dense masses on the flat places and on 

 the sloping piles of volcanic dust, sand, and loose rocks below the 

 cliffs. As we walked up these slopes the murres began pouring off the 

 rocks above us, sweeping down by us in steady streams, stumbling, 

 scrambling, and bounding along over the rocks and stones, in their 

 frantic efforts to get awing, a ludicrous performance; and down 

 with them came a shower of eggs, dislodged in their haste, rolling 

 or bounding along to smash on the first rock they struck. Plenty 

 of birds still remained in the rookeries, however, and if we kept 

 still the others would soon return after circling about us in a be- 

 wildering cloud. They were very tame as a rule and, if approached 

 cautiously, could almost be caught by hand ; we had no difficulty in 

 knocking them over with sticks. When undisturbed they usually 



