THE DUCK FAMILY. 21 



glands, and the overlying feathers, which are constant- 

 ly kept oiled, protect the down beneath them from mois- 

 ture and form a covering whose warmth enables the 

 birds to endure an Arctic temperature. There is a great 

 variety in the coloring of the plumage. The sexes in 

 the swans and most geese are alike, but in the ducks the 

 male is usually more highly colored than the female. 

 The males of some species are among our most beauti- 

 ful birds, as the mallard, harlequin, wood duck and the 

 odd little mandarin duck of Eastern Asia, while in 

 others the colors are duller, and in the female and 

 young are often extremely modest and subdued. Most 

 of the fresh water ducks possess a patch of brilliant 

 iridescent color on the secondary feathers of the wing 

 which is usually either green or violet. This is called 

 the speculum. A less brilliant speculum is seen in some 

 of the sea ducks. 



The males of certain species possess peculiar devel- 

 opments of plumage or of bill, such as the curled tail 

 feathers of the mallard, the long pointed scapulars and 

 long tail feathers of the old squaw and the sprig-tail, 

 the peculiar wing feathers of the mandarin duck, the 

 stiff feathers on the face in some sea ducks, the crests of 

 many species, and the singular processes and swellings 

 on the bills of certain sea ducks. 



The Duck family is divided into three sections — the 

 Swans, the Geese and the Ducks proper. These last 

 again are subdivided into shoal water or river ducks, 

 and sea or diving ducks. 



The swans are characterized by their large size and 



