ACTIVE GLEANERS 
127 
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, Phcebes, 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 
