Nest-Building Behavior in PCB-Contaminated Tree Swallows

Considerable attention has been directed toward documenting the effects of environmental chemicals on the endocrine systems of vertebrates, especially on development and reproduction. Given the well-documented role of hormones in controlling behavior, one would expect to see abnormal behavior in contaminated wildlife. We describe abnormal nest-building behavior in Tree Swallows (Tachycineta bicolor) breeding along the Hudson River of New York in areas highly contaminated with polychlorinated biphenyls (a group of chemicals known to disrupt endocrine systems). Previous studies of Tree Swallows have shown that nest quality is an important component of reproductive success. Swallows breeding in contaminated areas built smaller nests of lower quality compared with those in uncontaminated areas. Our observations are consistent with the possibility that chemical contaminants interfered with behavior.