LIFE HISTORIES OF NORTH AMERICAN PETRELS AND PELICANS. 81 



attracted my attention, and a closer examination revealed the unmistakable 

 tracks of a Puffinus. Tliough the footprints were abundant and fresh, prov- 

 ing that the burrows were still visited at night, all of those examined were 

 unoccupied. I again called at Natividad April 10, 1897, and found the breed- 

 ing season at its height, each burrow containing either a pair of shearwaters 

 or one shearwater and a fresh egg. In no case, I think, did I find an egg in 

 a burrow with two birds. The burrows were usually about ten feet in 

 length, seldom if ever straight, but with one or two sudden turns to the right 

 or left, the nest sometimes being but two feet from the entrance, though at 

 the end of a ten-foot burrow. Few of the nests were over eighteen inches 

 below the surface, the burrows being for the most part nearly horizontal, and 

 the loose nature of the soil made walking anything but a pleasure, as one 

 constantly broke through into tunnels the exact location of which it was 

 impossible to determine. 



The tracks in the fresh soil about the entrance to the burrows showed the 

 imprint of the tarsus for its full length, showing that the birds rest their 

 weight on the tarsus as much as on the toes. 



There was little attempt at nest-building, the eggs for the most part being 

 laid in a depression in the sand at the end of the burrow. In a few cases a 

 number of small twigs and sticks had been placed in the hollow, forming a 

 very crude nest. Before the egg is deposited the burrow is occupied by both 

 birds, and I have found them on the nest at least a month before any eggs 

 were laid. Just how early they take to the burrows I am unable to say, not 

 having visited the nesting colony earlier than the first week in March, when 

 all the burrows were occupied. 



Eggs. — The single egg of the black-vented shearwater is not very 

 different from the eggs of other species of the genus Puffinus. In 

 shape it is elliptical ovate or elliptical oval. The shell is somewhat 

 pitted but fairly smooth and not glossy. The color is pure dead 

 white. The measurements of 38 eggs, in various collections, average 

 G0.9 by 41.2 millimeters ; the eggs showing the four extremes measure 

 69 by 40, 60.5 by 43.5, 56.6 by 41.4, and 62.8 by 38.6 millimeters. 



Plumages. — The young bird remains in the nesting burrow until 

 it is fully fledged, which is not until it is fully grown also. It is 

 covered for the first few weeks with long soft down, varying in 

 color from " light drab " to " pale smoke gray " below. The first 

 plumage begins to appear late in June or early in July. Mr. An- 

 thony (1900) says of this plumage : 



On July 1, I found the burrows on Natividad occupied entirely by young 

 birds that were nearly or quite as large as the adults, but still clothed in down, 

 through which were growing a few feathers. They were sooty black above 

 and lighter below. When brought to the light they gave vent to their feelings 

 in the characteristic notes of the adults. 



The first plumage of the young bird is apparently similar to that 

 of the adult and probably the seasonal changes do not produce any 

 distinctive plumages. Mr. Leverett M. Loomis (1900), however, 

 says: 



In certain black-vented shearwaters (apparently immature birds) the white 

 of the lower parts is also invaded by gray, the jugulum and throat being mot- 



