The Black-vented Shearwater 



Authorities. — Ridgway {Puffin us gavia), Proc. U. S. Nat. Mus., vol. iii., 1880, 

 p. 223 (coast of Calif.); Anthony, Auk, vol. xiii., 1896, p. 223 (habits, nesting, etc.). 



NONE of the larger species of Petrels nest along our coasts; but opis- 

 thomelas is such a near neighbor when at home, and so frequent a visitor 

 at other times, that we claim the right to make careful inquiry as to his 

 appearance and conduct. Of its external aspect we need only say that it 

 is black above and white below with a sooty crissum, and that it is the 

 smallest of the four commoner species of Shearwaters which frequent our 

 coast. It is highly gregarious, and R. H. Beck, writing from Monterey, 

 regards it as only less abundant than the Sooty Shearwater (P. griseus). 

 Its abundance increases as we go southward, and vast companies of un- 

 mixed opisthomelas occur off San Pedro or San Diego Bay. 



To Mr. A. W. Anthony, then of San Diego, who in the Nineties made 

 such a careful study of pelagic bird-life off the coasts of southern and Baja 

 California, we are indebted for our only intimate knowledge of this 

 species. 1 He encountered them as breeding birds first on the island of 

 Guadalupe, which lies some 220 miles south of San Diego and 65 miles 

 offshore. Here, in company with Cassin Auklets and Xantus Murrelets, 

 they occupy thousands of vapor-holes and miniature caves which honey- 

 comb gigantic lava cliffs 3000 feet in height. Mr. Anthony was first 

 attracted to their presence by the sound of familiar notes heard in the 

 early evening, as his schooner lay at anchor beneath these crags. The 

 outcry soon increased to an uproar. "It would be impossible to describe 

 accurately these notes. They were a series of gasping wheezy cries, re- 

 sembling somewhat the escape of steam through a partly clogged pipe, 

 uttered in a slightly varied key and repeated from four or five, to ten 

 times. During calm weather in January, February, and March flocks of 

 a dozen to several hundred of these Shearwaters often collect on the water 

 well offshore and at such times I have heard the same notes from two or 

 more birds as they chased each other, half running, half flying, over the 

 water. From the notes that came from the cliffs I thought that the birds 

 were chasing one another, and a little later many of them came down to 

 the water and were occasionally seen as they flashed by our anchor light. 

 After an hour or so the outcry somewhat subsided and I think most of 

 the birds went offshore to feed, returning before daylight, for during 

 nearly two weeks spent cruising about the island only one flock of Shear- 

 waters was seen during the daytime." 



The observer later found that the Shearwaters were silent in their 

 burrows, but repeated their outcries as often as they emerged at night, 

 or were disturbed by intruders. 



1 As set forth in "The Auk," Vol. XIII., 1896, pp. 223-228; and Vol. XVII., 1000, pp. 247-252. 



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