THE DUCK TRIBE 2089 



distinguished by the marked inflection of its lower extremity. The first toe, 

 although generally small, is always present; while, as in the flamingoes, the three 

 front toes are, except in one instance, completely webbed. The relatively-short 

 beak is comparatively straight, and more or less depressed and laterally expanded, 

 with peculiar laminations on its edges; while the rostrum of the lower surface of 

 the skull shows well-marked basipterygoid facets for the articulation of the ptery- 

 goid bones. In the skeleton of the body the metacoracoid is much longer and nar- 

 rower than that of the flamingoes, and is also much less firmly articulated to the 

 breastbone. The plumage is characterized by its dense and compact nature, and the 

 facility with which water is thrown off from its surface. In the wings there are 

 always ten primary quills, but the number of tail feathers is liable 

 to variation. All the members of the order molt annually in the 

 autumn, and the quills of the wings are generally shed so rapidly 

 as to incapacitate the birds for flight for some days. In the true 

 ducks, however, the males change their contour feathers twice 

 in the year. Although the ducks resemble the flamingoes in 

 laying uniformly-colored eggs, they differ in that the number 

 in a clutch is large, instead of being generally but a pair; the 

 eggs themselves are further characterized by their hard and usu- 

 ally very smooth shells. 



The general external appearance of the members of the 

 duck tribe is too well known to need special mention. It may 

 be observed, however, that their build is the best adapted for 

 rapid progress through the water, the breast and fore part of 

 the body being broad and rounded, the hinder extremity narrow 

 and tapering, and the legs placed relatively far back. 



Although it has been attempted to divide the members of FRONT AND I.OWER 

 the order into several distinct families, the whole of them are VI EWS OF THE RIGHT 



i 11- J ^ L -^ -ui ^r. CANON BONE OF A 



so nearly allied that it seems impossible to do more than group DUCK 

 the genera of the one family Anatidtz under several subfamilies, 

 and even some of these are very difficult of definition. The species of the family, 

 which are probably about one hundred and sixty in number, are distributed all over 

 the globe, although more numerous in the higher latitudes of the Northern Hemi- 

 sphere than elsewhere. All are thoroughly aquatic in their habits; but while the ma- 

 jority are swimmers, the members of one group are expert divers. As a rule, they 

 associate in flocks of larger or smaller size, and migrate in numbers to the northern 

 portions of their habitat for the breeding season. They are all birds of strong 

 flight, and when on the wing fly in the well-known chevron -shaped formation, fre- 

 quently at a great height in the air. Although the majority of the species are more 

 or less omnivorous in their diet, the mergansers subsist exclusively on fish, while 

 the greater part of the food of the geese consists of grass. The group is not a very 

 ancient one, the earliest known forms occurring in the lower beds of the Miocene 

 division of the Tertiary period. 



The African spur- winged geese (Plectropterus} , of which there are two species, 

 take their name from the long spur on each wing, which is sharply pointed and 



