198 BRITISH SEA BIRDS. 
the Ducks in this sub-family habitually dive for 
their food, and their movements in the water are 
remarkably agile. The sexes generally present 
considerable difference in colour, the males, as 
usual, being the most handsome and conspicuous. 
The young are always hatched covered with down, 
and soon able to accompany their parents on the 
water. The females have a single moult in autumn, 
but the males a partially double one. Diving 
Ducks, in fact all species in the family, in first 
plumage, closely resemble the old female, and 
acquire the adult plumage after the first autumn 
moult. We will deal first with the resident species, 
as being constant features in the bird life of the 
coast and sea. 
EIDER DUCK. 
No Duck is more thoroughly attached to the sea” 
than this species, the Axas mollissima of Linnzeus 
and Latham, but the Somaterza mollissima of most 
modern ornithologists. Unfortunately it is some- 
what restricted in its distribution, only breeding in 
one locality on the English coast, occurring more or 
less accidentally elsewhere. Ireland is not even so 
fortunate, for no nesting station is known round the 
entire coastline of the island. The Eider Duck is 
a decidedly northern bird, and is found, if somewhat 
locally, round the coasts of Scotland, extending to 
the outlying islands, including St. Kilda, where I 
have taken its nest. To most people, perhaps, the 
down of the Eider Duck, in the form of a coverlet, 
