. The bird, its form and function . Fig. 305.—Rough-legged Hawk in position of defence. A duck or swan out of sheer laziness will often holdone foot up out of the water and propel itself with theother, slightly altering the angle at which the web meetsthe water, so as to maintain a perfectly direct is a little-known habit which I have frequentlyobserved in captive ducks and several times in wild ones,of swimming thus with one foot when both eyes are shutand the bird is apparently fast asleep. But, in such a 390 The Bird case, no attempt is made to proceed in a straight a p
. The bird, its form and function . Fig. 305.—Rough-legged Hawk in position of defence. A duck or swan out of sheer laziness will often holdone foot up out of the water and propel itself with theother, slightly altering the angle at which the web meetsthe water, so as to maintain a perfectly direct is a little-known habit which I have frequentlyobserved in captive ducks and several times in wild ones,of swimming thus with one foot when both eyes are shutand the bird is apparently fast asleep. But, in such a 390 The Bird case, no attempt is made to proceed in a straight a pool only thirty feet square I have seen a duckrevolving thus for an hour or more at a time, impelledwith slow, rhythmical (and apparently reflex) strokes. We. Fig. 306.—Foot of Black-necked Swan. can imagine that such a habit would sometimes be of muchadvantage to a wild bird, enabling it to keep away fromenemies on the shore and yet at the same time secure name Steganopodes is applied to the gannets,pelicans, snake-birds, tropic-birds, and cormorants, be- Feet and Legs 391 cause the toes of these birds are all bound together witha single web. The hind toe points almost in a forwarddirection when the foot is in action, and, to completethe adaptation for a perfect swimming foot, the outertoe is the longest, a rare condition among birds. If onewill watch the snake-birds in a zoological park, as theyswim about their glass tank, the extreme delicacy of thefoot mechanism becomes apparent at once. Not only is the flat side of the leg used as a cutwater,but the toes curl and uncurl with a slight oblique revolvingmotion like the blades of a propeller. When drawn for-ward through the water they are rolled up into a verysmall compass and t
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbirds, bookyear1906
