174 GREAT AUK. 
two latter and the sides of the head are white in autumn 
and winter. Breast, white; back, glossy black. 
Greater and lesser wing coverts, black; primaries, black, 
the longest quill feather is only four inches in length; 
secondaries, black, their tips white, forming a boundary to 
the wing; tertiaries, black; greater and lesser under wing 
coverts, white. Tail, black; upper tail coverts, black; under 
tail coverts, white. The legs, short, and placed far back, 
are, as the toes and claws, blackish; webs, blackish brown. 
Selby says that this species undergoes a double moult, 
and Dr. Fleming noticed that the change took place in a 
few days. 
In the young bird it would appear that the bill becomes 
only gradually grooved, and the neck is mottled with black 
and white. 
