188 BRITISH: SEABIRDS. 
dozen sub-families, all but one of which are repre- 
sented at some time of the year on our seaboard. 
The most important external characteristics of the 
birds in this family are the peculiar laminated bill, 
the short legs, the webbed feet, and the dense com- 
pact plumage. The family is almost cosmopolitan 
in its distribution. ' 
NON-DIVING DUCKS. 
Representatives of no less than three of the four 
sub-families into which the Ducks have been divided - 
by systematists, are found on the British coast-line. 
Each sub-family contains some thoroughly marine 
species. We will deal first with the Anatinz, con- 
taining the Sheldrakes and non-diving Ducks. The 
birds in this sub-family are distinguished from all 
others by having the tarsus scutellated or plated in 
front, and by having only a narrow membrane 
attached to the hind toe. A peculiarity about these 
Ducks is that they never dive for their food. This 
is obtained only in shallow water, by submerging 
the fore half of the body and dabbling and probing 
amongst the mud and weeds. In the Sheldrakes 
the sexes are nearly alike in colour, but in the 
remaining species there is usually considerable 
difference in this respect, the males or drakes 
being handsome, showy birds, the females or ducks 
brown and comparatively sombre-looking. The 
Sheldrakes moult once in autumn, the remaining 
species the same, but the drakes of these latter 
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