Removal of banded cowbird nestling by veery

TitleRemoval of banded cowbird nestling by veery
Publication TypeJournal Article
Year of Publication1956
AuthorsAnnan O

In the course of a nesting study of the Veery (Hylocichla fuscescens) made at UMBS, at Douglas Lake, Cheboygan County, Michigan, in July, 1956, I banded a young Brown-headed Cowbird (Molothrus ater). At that time, the nest contained two Cowbirds, which had hatched July 4, and one Veery, which had hatched July 5, as well as one Veery egg. Cowbirds do not commonly parasitize Veery nests, and I was interested in how it would work out. I had heard that birds sometimes removed banded nestlings, so, on July 8, and 6:30 p.m., I banded just one of the two Cowbirds. I put a Fish & Wildlife Service band on the right leg, and a red plastic band on the left. At this stage in the care of their young, the parent Veeries waited a few seconds after feeding the nestlings and then picked up and swallowed the fecal sac or sacs. One hour after the Cowbird was banded, the parent Veery remained on the rim of the nest after swallowing a fecal sac, and made ten vigorous efforts to pick something up from the floor of the nest, but was unsuccessful. Half an hour later, the parent again tried to pick up some object, and this time was persistent. I guessed what was happening, and kept count of the number of times the Veery reached into the nest. After about 15 tries, I could see that the bird was pulling on a leg. By the 39th try, the leg was pulled high enough so that I could see the aluminum band shining on it, looking white, like a fecal sac. At this time the young Cowbird began to make a noise. The Veery kept on pulling, until it had tried 50 times to lift the Cowbird out of the nest. Then it stopped, and sat still on the rim, cocking its head and peering into the nest. After about 15 seconds, it resumed its efforts and tugged with even more force, judging from the way its feet were braced. On the 65th try, the adult Veery dragged the young Cowbird from the nest and dropped it. Then the Veery flew heavily off with the nestling, settling to earth about ten feet from the nest. One more flight carried the birds out of my sight. At the time of removal, the young Cowbird weighed about 12 grams. The fact that the Veery's attention was directed entirely to the leg with the aluminum band, rather than to the leg with the red band, makes it seem possible that the color of the band, being similar to that of a fecal sac, released a removal response in the parent. In connection with this, it is interesting to note that immediately after carrying the young Cowbird off, the Veery returned, looked the nest over, impaled the remaining egg (which at this time was three days overdue), and flew off with it. The bird then returned, looked in the nest (putting its head in the nest 13 times), and flew off. The remaining Cowbird, and the young Veery, survived to leave the nest on July 14, aged ten days and nine days respectively.