388 
Birds. 
in large flocks to more southern countries; and their 
clang is heard from the regions of the clouds, although 
the birds are out of sight. 
THE DUCK. (Anas bosdias.) 
The common Duck is of two kinds, the wild and the 
tame, the latter being but the same species altered by 
domestication ; the difference between them is very 
trifling, save that the colour of the Mallard, or male 
wild Duck, is constantly the same in all the individuals, 
whereas the Drakes, or tame ones, are varied in their 
plumage. The females do not share with the males in 
beauty of plumage : the admirable scarf of glossy green 
and blue, which surrounds the neck of Drakes and Mal- 
lards, being an exclusive prerogative of the male sex. 
There is also a curious and invariable peculiarity be- 
longing to the males, which consists of a few curled 
feathers rising upon the rump. 
