Effect of Stand Width and Adjacent Habitat on Breeding Bird Communities in Bottomland Hardwoods

Abstract

Bottomland hardwood forests support an abundant and diverse avifauna, but area of this forest type has been reduced, and current projections indicate continued declines. We compared breeding bird abundance indices and species richness among bottomland hardwood stands ranging in width from 1,000 m and enclosed by forested habitat. We also compared avian abundance indices and richness among stands enclosed by pine (Pinus spp.) forest and stands enclosed by field-scrub habitats. Total species richness and species richness of Neotropical migrants were associated positively (P 1,000 m. Counts of Neotropical migrants differed (P < 0.05) among width classes in 1993 and 1995 and followed the same general trend as total bird count. Acadian flycatcher (Empidonax virescens), blue-gray gnatcatcher (Polioptila caerulea), and red-eyed vireo (Vireo olivaceous) were more abundant in smaller width classes (P < 0.05), whereas the opposite was true for white-eyed vireo (Vireo griseus) and northern parula (Parula americana). Probability of occurrence was associated positively (P < 0.05) with stand width for 12 species and negatively with stand width for 1 species. Total bird count and the counts of blue-gray gnatcatcher in 1995 and of northern cardinal (Cardinalis cardinalis) in both years were higher in field-enclosed stands (FES) than in pine-enclosed stands (PES). No species analyzed was more abundant in PES than in FES. We conclude that even narrow riparian zones can support an abundant and diverse avifauna, but that conservation of wide (≥500 m) riparian zones is necessary to maintain the complete avian community characteristic of bottomland hardwood forests in South Carolina.