Effects of forest management on population parameters and habitat use of wood thrushes

Conroy, Michael; Krementz, David

Several species of neotropical migrant songbirds (NTMB) apparently have decreased in abundance in recent decades (Hall 1984, Wilcove and Terborgh 1984, Robbins et al. 1989, Askins et al. 1990, Finch 1991, Sauer and Droege 1992, Böhning-Gaese et al. 1993). For example, North American Breeding Bird Survey (BBS) data show that wood thrush (Hylocichla mustelina) populations in eastern U.S. forests have exhibited declines of 1.9% per year (P < 0.001) during 1966-88, (Sauer and Droege 1992) and declines of 1.8% per year (P < 0.001) during 1996-95 (Sauer et al. 1996). Wood thrush populations showed the most marked decline from 1978-88 (4.1%, P < 0.001; Sauer and Droege 1992). Two main causes for the apparent decline of some neotropical migratory birds (NTMB) have been proposed: (1) fragmentation and isolation of breeding forest tracts in North America and (2) deforestation of the neotropical wintering grounds. The interactive effects of wintering and breeding ground habitats on songbird populations are complex (Morse 1980, Temple and Cary 1988, Terborgh 1989), but the study of NTMB in these regions is a crucial management response to the population decline. The goal of our research is to determine the effects of a specific type of forest management on survival, movements, and habitat use of breeding adult wood thrushes in an experimental context. The experimental results should be helpful to wildlife managers in the southeast U.S. as they develop forest management plans.