The song of the Chestnut-sided Warbler is confused in the minds of some listeners with that of the Yellow Warbler. Mathews says the song resembles the words, “I wish, I wish, I wish to see Miss Beecher.”
Mr. Clinton G. Abbott, writing in Bird-Lore in 1909, told most entertainingly of the fortunes of a pair of these Warblers and their nest, which he watched one summer. After telling of finding a nest from which all the eggs had been thrown but one, and in their place had been deposited two eggs of the Cowbird, he says:
“The nest was found at Rhinebeck, New York, on July 6, 1900, incubation having apparently just started. Four days later I discovered that one of the Cowbird’s eggs was infertile; so I removed it from the nest, disappointed that I should not, after all, enjoy the somewhat unique experience of observing two young Cowbirds growing up in the same nest. It was some time during the night of July 13-14 that the first of the remaining two eggs hatched—the Cowbird’s of course. The Warbler’s hatched between twelve and twelve-thirty o’clock on the 14th. The nicety with which matters had been so arranged that the young Cowbird would have just a convenient start in life over its unfortunate rival commanded at least my admiration if not my sympathy. Cowbirds must indeed be sharp nest-finders to be able to discover at short notice not only the nests of certain suitable kinds of birds, but even nests containing eggs at a certain stage of incubation!
A NEST OF THE CHESTNUT-SIDED WARBLER
“After the hatching of the eggs, I spent considerable time at the nest-side, and observed with interest the many pretty little incidents of a bird’s domestic life—the constant and tender brooding of the newly hatched young by both Warblers in turn; the never-ceasing search among the neighboring trees and bushes for small caterpillars; the delivery of the food by the male to the brooding female, who, in turn, would raise herself and pass it to the young; the careful cleansing of the nest; and many other intimate details of the birds’ loving and happy lives. When I drew aside the leaves that sheltered the nest and allowed the sun to shine upon it for purposes of photography, the mother, realizing with that wonderful instinct common to all birds which nest in the shade, the fatal effect on her babies of the sun’s direct rays, would take her stand on the edge of the nest and with outstretched wings would form of her own body a living shield for the comfort and protection of her young. Although herself in evident distress from the heat, and with parted mandibles continually gasping for air, she would remain in this position as long as the sun shone upon her, only stepping aside occasionally when a well-known signal announced that her husband had arrived with a meal for the little ones. It was a beautiful picture of parental devotion.
“As the young birds began to grow, the Cowbird not only maintained, but rapidly increased its lead over its small nest-mate. At every visit of the parent bird with food, its capacious gullet could be seen violently waving aloft and almost completely hiding the feeble little mouth of the Warbler, whose owner was pathetically doing its best in a dumb appeal for food. The Cowbird’s appetite seemed never to be satiated and, unlike most nestlings, which relapse after a meal and give their brethren the next chance, he seemed ready for every fresh opportunity; and, by reason of his superior display, he usually succeeded in obtaining the coveted morsel. However, the young Warbler did manage to get an occasional portion, and I had strong hopes that he might reach maturity. For I realized that a Chestnut-sided Warbler’s usual laying is about five eggs, and that therefore some four eggs must have been made to give place to the two Cowbird’s. Hence the young Cowbird in the nest might reasonably be granted the room and food of four young Warblers. More than this I hoped he was not getting.
“On July 18, at 3.30 P. M., when the birds were about four days old, I took them from the nest to compare their sizes. I replaced them in the nest, but that was the last I saw of the poor little Warbler. When I returned at 5 P. M., the Cowbird was in sole and triumphant possession of the nest. Just what became of the Chestnut-sided Warbler will never be known, but my theory is that, weakened by lack of sufficient food, the little fellow at last became too feeble to raise himself at all, and was crushed to death by the Cowbird’s gross body. The parent birds, returning and finding the little corpse in the bottom of the nest, were no doubt impelled by their instinctive sense of cleanliness to carry it to a distance; for the most careful search over a large area beneath the nest failed to reveal any sign of the missing bird, thus proving that it had not fallen from the nest nor been forced out by the Cowbird.
“The Cowbird now had things all his own way and, there being no one to dispute his right to all the food, he grew with amazing rapidity. The dainty little cup of a nest, never built to accommodate such a monster, was soon completely forced out of shape. His body then protruded beyond the lower rim of the nest, and the ground underneath became littered with droppings, quite baffling the cleanly, sanitary instincts of the Warblers.