Mar., 1919 NESTING OF TWO SPECIES OF PETREL 61 
The nesting burrows of this petrel were in sandy soil in nearly all the drier 
parts of the island. They were generally from six to ten inches in diameter at 
the mouth, and seven or eight feet in length; it is very probable that part of 
this extensive excavation is done by the Wedge-tailed Shearwater (Puffinus 
cuneatus), as these birds are known to use the same burrows later in the sea- 
son. The shallow nest cavity at the end of the burrow is generally fairly well 
lined with grass and leaves. An exceptional nesting site of the species was 
noted on January 25, when a nest and egg were found under an overturned 
basket near the cabin. The single egg is pure white, unmarked. Six typical! 
eggs measure (in inches) as follows: Largest, 1.98x1.45; smallest, 1.85x1.42; 
average, 1.91x1.44. 
Heavy sandstorms during early February filled up several thousand bur- 
rows of this species, smothering many of the incubating birds. While walking 
among the colonies at this time, birds were frequently found imprisoned in 
sand at the mouths of burrows, often with their heads above the surface and 
still alive. 
Tne Sooty Petrel (Oceanodroma tristramz) at the time of our visit to the 
islands, was considered one of the rarest of the petrels, being known from a 
very tew specimens. We were therefore much pleased to find a substantial 
breeding colony on Laysan Island, also a smaller one on Pearl and Hermes Reef. 
A series of the birds was secured and, as little has been previously published 
regarding the species, the measurements obtained may be worthy of record. Ii 
will be noted that the females are appreciably larger than the males, in mosi 
instanees this being clearly perceptible in living birds. 
The average measurements (in inches) of six breeding males follow. 
BHength, 9:98; wing, 7.09; tail, 4.07,,..The largest measures: Length, 10.20; 
wing, 7.25; tail, 4.27. The smallest: Length, 9.40; wing, 6.68; tail, 3.77. Six 
breeding females average: Length, 10.39; wing, 7.48; tail, 4.33. The largest 
measures: Length, 10.92; wing, 7.61; tail, 4.58. The smallest: Length, 10.15, 
wing, 7.32; tail, 4.25. 
The nesting colony of the Sooty Petrel on Laysan Island was situated 
along the shores of the shallow salt-water lagoon that hes approximately in 
the center of the island. A rise in the water of this lagoon, caused by heavy 
rainfall February 6, flooded and destroyed several hundred of the petrels’ 
nests, as well as numerous nests of the Laysan Albatross (Diomedea immutabi- 
lis), One of the sand storms previously mentioned, coming two days later, also 
destroyed many nests by filling the burrows with sand. Probably at least half 
of the petrel colony was wiped out by these two catastrophes. 
The burrows of the Sooty Petrel were much smaller than those of the 
White-breasted, averaging about five inches in diameter and from two and one- 
half to three and one-half feet in length. In most instances they were quite 
crooked, resembling in this respect nesting burrows of Oceanodroma leucorhoa 
or O. furcata. The nest at the end of the burrow was composed of rootlets, 
weedstems and leaves. The eggs, deposited mostly during the first two weeks 
in January, are typical of the genus Oceanodroma, though, of course, larger 
than those of any of the genus along our Pacific coast, being approached in 
size only by those of O. macrodactyla, of Guadalupe Island. They are creamy 
white in color, more or less faintly dotted, scrawled or wreathed, with purplish 
and pinkish brown, mostly around the larger end. Average measurements (in 
inches) of six eggs are: 1.52x1.07; largest, 1.63x1.08; smallest, 1.48x1.07. 
Los Angeles, California, December 6, 1918. 
