160 BULLETIN 107, UNITED STATES NATIONAL MUSEUM. 
grayish below. They remain hidden among the rocks until the 
juvenal plumage is acquired in August; this is sooty black above and 
white below heavily mottled with dusky on the sides, less heavily 
on the belly and breast, and only very finely spotted on the throat 
and chin. The white wing patches are much concealed by the broad 
dusky tips of the feathers. The juvenal plumage is soon replaced 
by the first winter plumage, which is similar to the adult winter 
plumage but with less white and more dusky; there is much more 
dusky on the head, and the white wing patches are broken by black- 
tipped feathers; this plumage is worn all winter, but is molted 
wholly or partly into the black plumage during the first spring. I 
believe that young birds molt later in the spring than adults and that 
the molt is often less complete than in adults, producing a variety 
of mottled black and white plumages. The change into the adult 
winter begins in August but is not completed until October or later; 
winter adults may be distinguished from young birds by the greater 
proportion of white, particularly on the head, and by the pure white 
wing’patches. The spring molt, which includes all but the wings and 
tail, is considerably prolonged or varies greatly in date with different 
individuals. Some birds acquire their full summer plumage as early 
as the 1st of February, but I have seen birds during the first week in 
May in practically full winter plumage, and have birds in my col- 
lection in various stages of molt taken as late as June 18. 
Food—On the coast of Maine the black guillemot feeds largely 
on rock eels (Gunellus gunnelius), small fish which can be found at 
low tide under loose stones. It also eats small mussels and other 
small mollusks, which it obtains by diving and swallows whole, sea 
insects, marine worms, shrimps, small crabs, and other small crus- 
taceans, which swim on or near the surface. Small fish are fre- 
quently included in its diet. Mr. Lucien M. Turner, in his unpub- 
lished notes on the birds of Ungava, says: 
The food of the birds is essentially marine, consisting of all manner of 
smaller crustacea. Several stomachs were opened and found to contain re- 
cently swallowed specimens of Mysis mixta only; no other food being apparent. 
Other stomachs contained only a semiviscid fluid of reddish, amber color, such 
as might result from the digestion of such food as that just mentioned. 
Behavior—The only note that I have heard this species utter is a 
faint, shrill, piping whistle which is apparently used as a call rather 
than an alarm note. When disturbed on its nest it emits a hissing 
note of protests. It is usually silent, however. 
Its flight is strong, swift, and direct, with rapid wing strokes, 
usually close to the water. In diving it flops under the surface with 
open wings, using them regularly in subaqueous flight. Dr. Charles 
W. Townsend writes to me: 
