Songbird Abundance and Avian Nest Survival Rates in Forests Fragmented by Different Silvicultural Treatments

Abstract

Abstract:Concerns over declining songbird populations have led to investigations of the effects of various silvicultural practices on breeding songbirds. Few studies published, however, have examined both songbird populations and avian nest success among harvesting treatments, particularly in forested landscapes. We conducted a study in the Monongahela National Forest of West Virginia during the summers of 1993 to 1996 to compare breeding‐bird abundance and daily nest survival rates among different sivicultural treatments: a two‐age treatment (a type of deferred removal in which 37–49 mature trees/ha remain after a harvest until the next rotation), clearcutting treatments 15 years after harvest, unharvested forest surrounding the harvested stands, and unharvested stands not adjacent to cuts. Abundance and daily nest‐survival rates did not differ among treatments ( p> 0.05) for four of the five species for which the most nests were found: Wood Thrush ( Hylocichla mustelina ), Rose‐breasted Grosbeak ( Pheucticus ludovicianus ), Acadian Flycatcher ( Empidonax virescens), Veery ( Catharus fuscescens ), Red‐eyed Vireo ( Vireo olivaceus ). Parasitism rates were low (6%), and most parasitized nests were associated with the two‐age harvest treatment. A source‐sink model for the Wood Thrush revealed that all treatments were likely population sources for this species. Thus, it appears that 15 years after harvest, cuts placed within otherwise extensively forested areas do not result in the type of edge effects (population sinks) observed in areas fragmented by agriculture in the midwestern United States. Further, because neither nest success nor avian abundance was lower in the two‐age than clearcut harvests, we conclude that two‐age management is a viable conservation alternative to clearcutting in large forested landscapes where Brown‐headed Cowbird ( Molothrus ater) parasitism is not a concern.