BIRDS IN THE CALENDAR 
breeding places of the eider duck, commer- 
cially the most valuable of all ducks. The 
nest is robbed of this down once before the 
eggs hatch out, with the result that the 
female plucks another store from her own 
breast, supplemented if necessary from the 
body of the drake. The sitting bird is then 
left in peace till the nest has fulfilled its 
purpose, when the remaining down is likewise 
removed. This down, which combines 
warmth and lightness, gives a high market 
value to the eider, which, throughout Scan- 
dinavian countries is strictly protected by 
law and even more effectually by public 
opinion. 
The majority of ornamental ducks inter- 
breed freely in captivity. Those who, ap- 
parently on reliable evidence, distinguish 
between the polygamous habit in tame ducks 
and the constancy of the mallard and other 
wild kinds to a single mate have hastily 
assumed that such hybrids are unknown in 
the natural state. This, however, is incorrect, 
as there have been authentic cases of crosses 
between mallard and teal, pochard and scaup 
and other species, such hybrids having at 
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