Response of birds to grazing of riparian zones

Livestock grazing of streams and associated riparian areas may negatively i mpact avian communities through direct disturbance and alteration of vegeta tion structure. We determined the effects of grazing on vegetation, avian a bundance, species richness, and reproductive success on pasture streams and associated riparian habitats in southwest Pennsylvania. Bird counts, nest monitoring, and vegetation sampling were conducted on 12 pairs (grazed and control) of streams in 1996 and 10 pairs in 1997. Compared with control str eams, grazed areas had lower avian species richness and abundance. Several wetland-and riparian-dependent species (e.g., common snipe [Gallinago galli nago], great blue heron [Ardea herodias], green-backed heron [Butorides str iatus], belted kingfisher [Ceryle alcyon] and solitary sandpiper [Tringa so litatia]) were found more often or only on control areas. Although nest den sity was higher and nest destruction rates by livestock were lower on contr ol streams, nest success (all species combined) was not affected by grazing . Avian communities in control areas appear to benefit primarily from impro ved vegetative cover and structure. Thus, management should focus on exclud ing livestock from such areas.