360 The Bird 
each foothold as secure as if its feet were vacuum- 
cupped. 
In the swallows the feet are very small, having fallen 
into disuse with the great increase of the power of flight. 
Orioles and weaver-birds make occasional use of their 
feet to hold a strand of grass or string which they are 
weaving with their beaks into their elaborate nests, and 
certain flycatchers pounce upon and hold their insect 
Fig. 288.—Swallow, showing small size of feet. 
prey as an owl grips a bird, or a jay clings to a nut; but 
with the exception of a few such cases, the feet of perching 
birds serve principally the function of locomotion. 
As variation in habitat or haunt depends so much upon 
the power of locomotion, it will not be out of place to 
mention here, in rather more detail than usual, a splendid 
example of adaptive radiation which we can all verify for 
ourselves. 
There is no more wonderful fact in Nature than the way 
