GHAP TER" Vi 
True Ducks. 
THERE is no single character marking off this sub- 
family, which includes the vast majority of species, as 
there exists init an infinite variety of form, adapting the 
birds to various conditions of hfe; some of the true 
Ducks being as much land-birds as the Geese, while 
others are as aquatic as the Mergansers, or even more 
so. Moreover, the plumage and even size varies im- 
mensely according either to species or sex. 
The members of this sub-family, however, may 
nevertheless be easily distinguished from those of the 
others by negative characters, as pointed out in my 
introductory chapter. They never have, like Swans, 
excessively long necks, nor equal a tame Goose in size ; 
nor (except in the Golden-eye) are the nostrils ever set 
as far from the root of the bill as from the tip, as in the 
Geese ; nor do their bills ever show the very narrow 
form found in the Mergansers, with the tip less than 
half as broad as the root. 
In most cases, however, the bill of a true Duck will 
at once distinguish it from any member of the family 
except a Swan, with which there is no danger of any 
contusion. A Duck’s billis normally broad and shallow, 
especially towards the tip, of which the nail, as a _ rule, 
forms the centre only and is turned down into a more or 
less marked hook ; the nostrils are near the base ; and 
the lower chap is so much smaller than the upper that 
it shuts quite into it, and cannot be seen from the side, 
while in most Geese and in Mergansers it is quite visible 
when the billis shut. Thesides of the bill are parallel, 
or it enlarges towards the end, tapering in a few 
