390 The Bird 
case, no attempt is made to proceed in a straight line. 
In a pool only thirty feet square I have seen a duck 
revolving thus for an hour or more at a time, impelled 
with slow, rhythmical (and apparently reflex) strokes. We 
Fic. 306.—Foot of Black-necked Swan. 
canimagine that such a habit would sometimes be of much 
advantage to a wild bird, enabling it to keep away from 
enemies on the shore and yet at the same time secure rest. 
The name Steganopodes is applied to the gannets, 
pelicans, snake-birds, tropic-birds, and cormorants, be- 
