Feet and Legs 391 



cause the toes of these birds are all bound together with 

 a single web. The hind toe points almost in a forward 

 direction when the foot is in action, and, to complete 

 the adaptation for a perfect swimming foot, the outer 

 toe is the longest, a rare condition among birds. If one 

 will watch the snake-birds in a zoological park, as they 

 swim about their glass tank, the extreme delicacy of the 

 foot 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 revolving 

 motion like the blades of a propeller. When drawn for- 

 ward through the water they are rolled up into a very 

 small compass and then instantly spread out as widely 

 as possible on the return stroke. To the eye it seems 

 as if the bird was constantly grasping something tangible 

 in the water and thrusting it behind. 



This propeller motion may be observed even better 

 in a captive grebe. If the bird's head is placed in a glass 

 of water, its feet will move back and forth in the air with 

 all the motion of swimming. The adaptation for swimming 

 in these birds is so fundamental and thorough that even 

 the claws are broadened and flattened until they resemble 

 finger-nails. On land, grebes are absurdly awkward, 

 although they can walk upright even up a slight incline. 

 But they are powerless to rise from the ground, even 

 with the aid of the wind, needing the greater speed which 

 a swimming take-off from the water will give them. 



The most aquatic of all birds, the penguins, make 

 much more use of their wings than of their feet in swim- 

 ming and diving. The toes are webbed, however, and 



