Width of forest streamside zones and breeding bird abundance in eastern Texas
We evaluated breeding bird communities in forested streamside zones in eastern Texas to determine threshold widths of riparian forest that were associated with the addition of mature-forest-breeding birds and loss of shrub-breeding birds. We observed an association of shrub-breeding birds with narrow streamside zones and an increasing number of mature forest species within wider streamside zones. Streamside zones also provided song perches for many shrub breeding species. Although many bird species increased or decreased in a generally linear pattern as streamside zone width increased, some species appeared to have threshold widths associated with their presence. The Acadian Flycatcher (Empidonax virescens), Yellow- throated Vireo (Vireo flavifrons), and Yellow-billed Cuckoo (Coccyzus americanus) seemed to require at least 70 m of forest width before their abundance increased. In contrast, the Blue Grosbeak (Passerina caerulea), Painted Bunting (Passerina ciris), and Prairie Warbler (Dendroica discolor) decreased markedly at widths greater than 20 m and were absent after streamside zone widths increased beyond 70 m. We were unable to detect a relationship between streamside zone width and abundance of 11 species of birds. Uncut forested streamside zones within pine plantations provided a variety of habitat for forest-breeding and shrub-breeding birds that would not have been present had streamside zones been cut during harvesting operations. Our results provide important information to help forest managers balance the habitat requirements of both shrub-breeding and forest-breeding birds when they harvest timber in southern pine forests.