Effects of Small Forest Openings on the Breeding Bird Community in a Vermont Hardwood Forest

Abstract

We examined the response of a forest bird community to the presence of small openings created by patch clear-cutting 0.4-ha plots within an extensive northern hardwood forest. We conducted bird censuses (June) and habitat measurements (July-August) in 102 census plots at four distances from openings in 1991 and 1992. Of 19 habitat variables measured, none differed significantly among forest plots at any distance from clear-cuts. Thirty-five (70%) of 50 bird species encountered during censusing were Neotropical migrants. Bird species richness did not differ as a function of distance from openings. However, species composition in plots within openings was least similar to that in plots farthest into forest, and most similar between the two distance categories farthest from openings. The movement of several forest-interior species away from openings, the addition of early-successional colonists in openings, and a high abundance of interior-edge species near openings contributed to the difference in species composition between openings and forest plots. As a group, Neotropical forest-interior migrants were significantly less abundant in openings than at any distance from them, and less abundant 50 m from openings than 200 m from them. Neotropical interior-edge migrants were significantly more abundant 50 m from openings than at any other distance. Nearctic migrants and nonmigrants did not respond to the presence of small openings. Of three locally common avian nest predators, none became more abundant in the openings. Brown-headed Cowbirds (Molothrus ater), also common locally, were never observed in or near the openings. Overall, bird species diversity increased in forested areas containing small openings due to the addition of edge and open-area nesters, but several forest-interior species were adversely affected by the presence of openings.