ACTIVE GLEANERS 137 



his perpetual energy and the occasional hurried call^ 

 given out without pausing in his work. 



The insect world may hold itself in check by the 

 parasitism that besets every species. Perpetual 

 warfare holds, controls, and restrains a possibility 

 of reproduction sufficient to devour the world's 

 vegetation. The balance of contending forces has 

 swayed but little during the comparatively brief 

 period covered by human observation ; and a lazy 

 summer hour watching the ceaseless activity of the 

 birds reveals their important part in the struggle 

 that holds insect life in check. They are indis- 

 criminate, it is true, feeding as freely on the useful 

 parasite as on the injurious leaf-eater ; but they 

 are an established element in the perpetual conflict, 

 and cannot be destroyed or removed without grave 

 danger. 



Birds destroy insect life in all its forms. Nowhere 

 are the insects safe. Woodcock, Snipe, and other 

 shore birds bore for them in the mud and sand. 

 Robins pluck them from the hard earth. Thrushes 

 turn over the leaves in search of them. Woodpeckers 

 bore into the trees for them. They are caught on the 

 wing by Kingbirds, Phoebes, Night-hawks, Swallows, 

 and even Warblers and Sparrows. Nuthatches and 

 Creepers search every crevice in the bark for them. 

 The nimble little Warblers go swiftly and patiently 

 over every branch, twig, and leaf, as if determined 



