110 BULLETIN 107, UNITED STATES NATIONAL MUSEUM. 
PTYCHORAMPERUS ALEUTICUS (Pallas). 
CASSIN’S AUKLET. 
HABITS. 
Like the preceding species, the Cassin’s auklet is nocturnal in its 
habits on its breeding grounds, as it is distinctly a pelagic species 
and comes ashore only to breed, coming and going under the cover 
of darkness. Yet it is decidedly the best known of the auklets, as it 
has by far the widest breeding range, from the Aleutian Islands to 
central Lower California, and it is an abundant bird all along our 
Pacific coast at all seasons of the year. 
Nesting. —It is probably migratory to some extent, but, as with 
most of the Alcidae, its spring and fall migrations consist mainly of 
a movement onto its breeding resorts in the spring and departure 
from them to the open sea in the fall. Prof. Harold Heath (1915) 
says that “the natives state that Cassin auklet arrives on Forrester 
Island about March 1,” as it begins nesting early. In his account 
of the nesting habits of the species on this island he states that he 
was unable to distinguish any external mark of identification between 
the burrows of the Cassin’s auklet and the ancient murrelet. 
It was accordingly impossible to determine the exact numbers of the two 
species. It can be said, however, that the Cassin auklet has been found to 
occupy several sites from the sea level to a height of 500 feet, and the presence 
of eggshell fragments in many places indicates théir general distribution over 
the island and in small numbers on Lawrie and South Islands. As in the case 
of the ancient murrelet, the openings of the burrows are located about the roots 
of trees, or beneath partially buried logs or stones. The tunnel itself ranges 
from 2 to 4 feet in length, and is usually only sparingly branched. Whether 
they occupy the same home season after season is not known. It is certain, how- 
ever, that several of the tunnels have been occupied at one time by mice, as is 
evidenced by accumulations of gnawed cones in some of the lateral galleries 
or in the material scraped from the main canal and accumulated about the 
entrance. 
On Forrester Island the duties of nest building are no more onerous than 
characterizes the species elsewhere. A few twigs of the Sitka spruce, together 
with old or mouse-eaten cones and occasional fragments of moss, appear to be 
all that is necessary. The length of the incubation period was not determined, 
though Captain John (a remarkably keen and accurate naturalist of the Haidah 
Tribe) says that it lasts “about two weeks.” Fully three weeks more are 
required to bring the fledgling to the time of departure from the nest. During 
the time of incubation the female occupied the burrow in five cases at least, 
and the Indians claim that she is fed during the night by the male and never 
leaves the nest until the young is several days old. 
One of the most populous colonies of this species is to be found on 
the Farallone Islands, of which Mr. W. Leon Dawson (1911) writes: 
The Cassin auklets are everywhere. Burrows predominate, but there is not a 
cleft, nook, crack, cranny, fissure, aperture, retreat, niche, cave, receptacle, or 
hidey-hole from the water’s edge to the summit of the light tower which is not 
