16 THE NIDOLOGIST 
Eggs of the Black, Socorro and Least 
Petrels. 
N ADVANCE of a more extensive article 
ov the lite histories of these little-known 
Petrels, I will give a brief description 
of their nesting habits, and describe their 
eggs, which have been until now unknown. 
On July 22 I anchored in the lea of the 
larger of the San Benito Islands, which lie 
about seventy-five miles off the coast of 
Lower California, and some twenty miles 
west of Cerros Island, between latitude 28 
deg. and 30 deg. 
The San Benito Islands are small, rocky 
reefs only, with little vegetation, and being 
so far off shore are but little resorted to by 
Gulls, Cormorants and similar species. Cas- 
sin’s Auklets had bred in considerable 
numbers, as their burrows testified, but at 
the time of our visit they had al! left. 
Their burrows, however, had been appro- 
priated by later arrivals, and during the four 
and a half days that we spent at the Island, 
Mr. Horace A. Gaylord and myself devoted 
most of our time to digging for Petrels. 
Both Black and Socorro Petrels were taken 
from the burrows formerly occupied by the 
Auklets, the former species out-numbering 
tke Socorro about five to one. There was 
no attempt apparently on the part of the 
species to colonize by themselves, both 
being found in adjoining burrows. The 
Socorro Petrel had evidently begun nesting 
somewhat earlier than its neighbor, the 
Black, for while fresh eggs of “the latter 
were the rule, very few fresh or even mod- 
erately incubated eggs of the Sorocco were 
found, and several downy young were 
taken. 
There was little if any attempt at nest 
building by either species, though in several 
burrows a small nest-like platform of little 
twigs was found upon which the egg was 
laid. But in most eases it rested upon the 
bare earth at the end of a more or less 
winding burrow, about three feet in length. 
Several eggs of both species were taken 
from under loose slabs of rock, but as a 
rule they preferred the burrows which were 
in all cases, I think, those of Cassin’s 
Auklet. 
On our return to the island, September 
8 and 9, we found that the Sorocco 
Petrels had all left, but many young Black 
Petrels were found, as well as a few eggs 
which the birds wers stz// zncubating. 
The fresh eggs of both species were white, 
with a slight rosy blush before being blown, 
but pure white after the contents were 
removed—the shell smooth without gloss. 
Those of the Black Petrels were in all 
cases spotless, but about half of the eggs 
of the Socorro were marked about the 
larger end by aring of pale lavender specks, 
often quite faint, but in some specimens 
well defined. Their shape was similar in 
both species, ranging from an elongate 
ovate to a short or even rounded ovate. 
The eggs of either species were easily iden- 
tified, however, by their size, ten speci- 
mens of Oceanodroma socorroensis averag- 
ing 30x27-7 millimetres, an unusually 
elongated specimen, measuring 33.2x22.5 
millimetres. Tenegegs of O. melanza averag- 
ed 35.2x26 millimetres. 
The second day on the island Mr. James 
M. Gaylord, the botanist of our party, 
reported finding a ‘‘half-grown Petrel incu- 
bating an egg’’ on another part of the 
island. Scarcely daring to hope but sus- 
pecting that it might be the almost mythical 
Least Petrel, he was instructed to bring it 
back with him when he returned from that 
quarter next day. As we had surmised, 
the specimen proved to be /alocyptena 
microsoma, which we subsequently found 
breeding in several parts of the island. All 
eggs of this species were taken either from 
under loose slabs of rock or crevices in the 
broken ledges, the former location seeming 
to be preferred. None were found in bur- 
rows, although several were opened in the 
colonies of thisspecies. They all contained 
either O. melania or O. socorroensis. 
In shape the eggs of the Least Petrel 
were more inclined to be elliptical than 
either of the other species described, but 
were often elongate-ovate, short or even in 
some cases rounded ovate as in the species 
of Oceanodroma. 
They were pure white, with rosy flush 
before being blown, but dead white after- 
ward. In many, if not in the majority of 
our specimens, a ring of very minute black 
specks encircled one or both ends. These: 
specks came off upon the slighest touch, 
leaving slight stains or marks such as might 
be made by brushing away a spot of lamp- 
black which had accidentally fallen on the 
shell. 
Eggs taken from July 24 to 27 were in 
most cases fresh or but slightly incubated, 
though many were well advanced in incu- 
bation. 
Downy young, and even incubated eggs 
