USE AND IMPORTANCE OF FEATHERS AS NEST LINING IN TREE SWALLOWS (TACHYCINETA-BICOLOR)

Tree Swallows (Tachycineta bicolor) commonly line their grass nests wi th feathers of other species. In one of three years studied, there was a significant negative correlation between numbers of feathers in the nest and chick nestling periods (i.e. broods surrounded by more feath ers fledged earlier). In the third year of the study, the population w as divided into two groups, balanced for all measurable aspects of par ental quality. In the ''removal'' group, all feathers were removed dai ly and in the ''control'' group all feathers were allowed to remain. A ll nests and their contents were disturbed equally. Chicks in removal nests had lower growth rates (in mass, wing chord and tarsus) and high er infestations of mites and lice. I suggest that feathers aid chicks directly by preventing hypothermia and indirectly through higher growt h rates by allowing earlier fledging when necessary. Protection from e ctoparasites may be an important advantage in natural nests where nest cavities are not cleaned out annually. Inadvertent removal of feather s from nest boxes may be an important cause of posthatching declines i n feather numbers.