. 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 w^ater 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 frequentlyobserv^ed 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
. 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 w^ater 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 frequentlyobserv^ed 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 Rlack-neckpd 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 Sfeganopodes is applied to the gannets,pelicans, snake-birds, tropic-birds, and cormorants, be- Feet and Legs ogi cause the toes of these birds are all Iwiind tofrether witha single web. The hind toe points almost in a forwarddirection when the foot is in action, and, to completethe adaptation for a perfect swdmming 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 fiat 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
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Keywords: ., bookauthorbeebewil, bookcentury1900, bookdecade1900, bookyear1906
