UTILITY OF BIRDS. 59 



sidered omnivorous, but I am convinced that during the 

 months of spring and summer, his diet consists almost entirely 

 of insects. 



The wren, the creepers and the tomtits seek their food by 

 creeping round the branches, and take less of their food from 

 the foliage than either the Sylvians or the Fly-catchers. They 

 seldom pause in their circuitous course, proceeding usually 

 from the junction of the branches to their extremity, then 

 hopping to another branch, and proceeding upwards till they 

 are satisfied and pass to another tree. The Sylvians always 

 appear to examine the leaves and blossoms, while the creepers 

 and tomtits examine more carefully the bark of the tree. 

 Hence the Sylvians do not prolong their stay with us after the 

 fall of the leaf, while the others are seen after the trees are 

 entirely denuded, leading us to infer that the one feeds chiefly 

 upon beetles and other insects which are most abundant in the 

 summer months, while the others subsist upon insects in their 

 embryo forms, which, during autumn and winter, are concealed 

 in the crevices of the bark of trees. 



The habits of the Fly-catchers are quite different from those 

 of any of the species I have just named. Let us take the 

 pewee for an example. He sits on the bough of a tree almost 

 motionless, except a frequent sidling of the head, indicating 

 his watchful condition. He does not seem to be so diligent as 

 the Sylvians ; but that he is not idle is shown by his frequent 

 flitting out, in an irregular circuit, and immediately returning 

 to his perch with a captured insect. These salient flights are 

 performed as often as once in four or five seconds, and he often 

 turns a summerset in the act of capturing his prey when it 

 tries to elude him. He seldom misses his aim, and probably 

 collects ten or fifteen insects every minute, of an appreciable 

 size. As he lives entirely upon them, and is also, in the early 

 part of summer, engaged in supplying the wants of his young, 

 this is no extravagant estimate. 



The pewee does not catch all his food while it is on the 

 wing, but he is always on the wing when he takes it. If he 

 sees a moth or a beetle upon a leaf or a branch, he flies to it 

 and seizes it while he is poised in the air. A Sylvian would 

 stand upon the branch and extend his neck forward to take it. 

 The Yireos, which form an intermediate genus between the 



