The Yellow Warbler
Jonathan Swift's epitome of the subject, if not specifically true, is at least correct in its general application:
"A flea
Has smaller fleas that on him prey;
And these have smaller still to bite 'em;
And so proceed ad infinitum."
Even the tiny egg of a butterfly has its ichneumon parasite, a microscopic wasp, which lays its own egg within the larger one, which ultimately hatches a wasp instead of the baby caterpillar.
But who ever heard of anything but good luck falling to the lot of cow-bird or cuckoo, except as its blighting course is occasionally arrested by the outraged human? They always find a feathered nest.
In this connection it is interesting to note certain developments in bird life upon the lines of which evolution might work with revolutionary effect. Most of our birds are helpless and generally resigned victims to the cow-bird, but there are indications of occasional effective protest among them. Thus the little Maryland yellow-throat, according to various authorities, often ousts the intruded egg, and its broken remains are also occasionally seen on the ground beneath the nests of the cat-bird and the oriole. The red-eyed vireo, on the other hand, though having apparently an easier task than the latter, in the lesser depth of her pensile nest, commonly abandons it altogether to the unwelcome speckled ovum—always, I believe, if the cow-bird has anticipated her own first egg.
A Blighted Home
But we have a more remarkable example of opposition in the resource of the little yellow warbler, which I have noted as one of the favorite dupes of the cow-bird—a deliberate, intelligent, courageous defiance and frequent victory which are unique in bird history, and which, if through evolutionary process they became the fashion in featherdom, would put the cow-bird's mischief greatly at a discount. The identity of this pretty little warbler is certainly familiar to most observant country dwellers, even if unknown by name, though its golden-yellow plumage faintly streaked with dusky brown upon the breast would naturally suggest its popular title of "summer yellow-bird." It is one of the commonest of the mnio-tiltidæ, or wood-warblers, though more properly a bird of the copse and shrubbery than of the woods.
