194 BULLETIN 107, UNITED STATES NATIONAL MUSEUM. 



to take their chances on the watery deep. After making the peril- 

 ous descent from the cliff the youngster is conducted by one or 

 both of its fond parents out onto the open sea, often far from land, 

 where it is well cared for until it learns to shift for itself. The 

 young murres with their parents leave Bird Eock so early in the 

 season, long before the other seabirds have left, that a visitor to the 

 rock in August would get the impression that very few of this 

 species had bred there. 



Plumages. — When first hatched the young Briinnich's murre is cov- 

 ered with a short, thick coat of soft down, which varies from " black- 

 ish brown " or almost black to " clove brown," " benzo brown," or 

 " snuff brown " on the upper parts, shading off to " mouse gray " 

 on the throat and sides; there is a broad, median whitish streak on 

 the breast and belly, but nothing like the extensive white under parts 

 of the downy young Uria troille; the head and neck are variegated 

 or mottled with many long, whitish or pale buffy filaments, which 

 are soon shed. Mr. William Palmer (1899) has given a full and 

 accurate description of the development of the downy young of the 

 Pallas's murre showing what becomes of these filaments. A soft 

 Juvenal plumage is worn until the young murre is nearly grown, 

 when it is replaced by the first winter plumage. This differs from 

 the adult plumage in being lighter brown on the back; the white of 

 the throat is usually more mottled with dusky, but there are no con- 

 stant plumage characters that I can find by which old and young 

 birds can be distinguished in the fall. The bill of the young bird, 

 however, is decidedly smaller and weaker than that of the adult. 

 At the first prenuptial molt, which occurs late in the winter or early 

 in the spring, young birds become indistinguishable from adults. 



Adults have a complete postnuptial molt beginning in August 

 but often prolonged until late in the fall, by which the partially 

 white throat of the winter plumage is acquired; the white of the 

 throat is usually much more extensive and less mottled with dusky 

 in old birds than in young. This plumage is apparently not worn 

 for a long time in old birds and is replaced by a partial molt into 

 the nuptial plumage during the winter, though the material avail- 

 able does not show this very clearly. 



Food. — The food of Briinnich's murre consists mainly of small 

 fish, crustaceans, and mollusks, which it obtains at sea both on the 

 surface and by diving, at which it is an adept. Mr. J. D. Figgins 

 writes to me that " their food consists largely of marine insects and 

 salmon-colored ovate eggs, or larvae, not determined." 



Behavior. — Its flight in the air is strong, swift, and direct, with 

 steady, rapid wing motion; its heavier, shorter build helps the prac- 

 ticed eye to distinguish it from Urla troille; and from Alca torda it 

 can be distinguished by the short neck and long tail of the latter 



