248 ANTHONY, Westing Habits of Shearwaters faly 
were all inaccessible owing to the nature of the sites selected, 
either in natural holes in the lava or under large boulders, and 
no eggs were-secured. A night was spent on the top of the 
island in a heavy cypress growth, about 4000 feet above the 
sea. Here the Shearwaters were heard all night, their choking, 
gasping notes coming from all sides as they flew through this 
grove. 
On the San Benito Islands, lying between Guadaloupe and 
Cerros Islands, I have also found a few P. ofzsthomelas nest- 
ing. So far as I have been able to discover, there are no bur- 
rows on these islands, all the nests being in small caves, which 
are nearly filled with deposits of guano left by untold generations 
of Puffinus. The caves are all small and the nests inaccessible 
but I think that each cave was inhabited by several pairs of birds, 
judging by the outcry and warning hisses that greeted my 
approach to the entrance. 
About thirty-five miles south of San Benito Islands lies 
Natividad Island, a lower and more sandy island than those pre- 
viously mentioned —a condition which seems to suit the require- 
ments of the Black-vented Shearwaters to a nicety, for here are 
found thousands of them, nesting the full length of the island, 
some three miles in extent. With the exception of a few rocky 
slopes and ridges the entire island may be said to be one almost 
continuous colony. This island I first visited in August, 1896. 
The size of the burrows at once attracted my attention, and a 
closer examination revealed the unmistakable tracks of a Puffinus. 
Though the footprints were abundant and fresh, proving 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 breeding 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 
