LIFE HISTORIES OF NORTH AMERICAN DIVING BIRDS. 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 recks 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—tThe 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 Rock, 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 
