Effects of White-Tailed Deer on Songbirds Within Managed Forests in Pennsylvania

White-tailed deer (Odocoileus virginianus) populations have been maintained at high densities in Pennsylvania for several decades with unknown effects on songbirds and their habitats. I evaluated effects of white-tailed deer density on songbird species richness, abundance, and habitat. I simulated 4 deer densities (3.7, 7.9, 14.9, and 24.9 deer/km2) within individually fenced enclosures on 4 65-ha forest areas in northwestern Pennsylvania. Within all enclosures, 10% of the area was clear-cut and 30% was thinned. Enclosures were subjected to 10 years of deer browsing, 1980-90, at the 4 simulated densities. I conducted bird counts in1991. Varying deer density had no effect (P > 0.1) on ground- or upper canopy-nesting songbirds or their habitat, but species richness of intermediate canopy-nesting songbirds declined 27% (P 0.01) and abundance declined 37% (P = 0.002) between lowest and highest deer densities. I did not observe the eastern wood pewee (Contopns virens), indigo bunting (Passerine cyanea), least flycatcher (Empido-na:r_ minimus), yellow-billed cuckoo (Coccyzus americanus), or cerulean warbler (Dendroica cernlea) at densities >7.9 deer/km2and the eastern phoebe (Sayornis phoebe), and American robin (Turdus rnigratorius) were not observed at24.9 deer/km2. Threshold deer density for effect on habitat and songbirds within managed (100-yr rotation)forests was between 7.9 and 14.9 deer/km2. This article was written by J Wildl for the U.S. Forest Service, Northeastern Forest Experiment Station.

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