Breeding Bird Relationships to Landscape Metrics in Coastal Plain Georgia

Some avian species in the southeastern United States are declining, and population decreases may arise from changes in vegetation type area or structural condition. Our objective was to compare abundance of conservation priority bird species with landscape variables. We found, even in the highly forested Coastal Plain of Georgia, that areal extent and core area of cover types were related to abundance for certain bird species. Acadian flycatcher and field sparrow had models that incorporated positive area variables. Downy woodpecker, northern parula, orchard oriole, prairie warbler, and summer tanager had models that included positive area and edge associations with varying scales and vegetation types. Edge appeared in models for red-bellied woodpecker, blue jay, and brown-headed cowbird. More than half of all species did not have models that met prediction thresholds. Systematic assessment of area requirements for declining species provides information for management, conservation, and research. 1. Introduction Populations of certain bird species in the southeastern United States are declining, particularly disturbance-dependent species associated with grasslands, shrublands, and open forests [1]. Population trends may arise from land use changes in vegetation type area or structural condition. Stand elements, including vegetation composition and structure, can affect a variety of bird species, such as cavity nesters that require older trees or early successional species that need an open canopy and midstory. Thus, availability of stand-level structural elements may also be related, cumulatively at the landscape scale, to abundance of some declining bird species. Most bird-landscape studies have taken place outside of the Southeast. Compared to regions with forests fragmented by agriculture and urbanization, Coastal Plain landscape research on breeding birds has been equivocal, perhaps because many patches of one forest type or stage are enclosed within forest of another type or stage [2, 3]. Such studies include Krementz and Christie [4], who detected no effect of clearcut size on species richness or juvenile to adult ratios in birds captured in mist nets. Aquilani and Brewer [5] determined that wood thrush (see Table 2 for scientific names) nest success was greatest in large fragments of vegetation types and least near clearcut edges, primarily due to varying predation levels. Edge increased nest predation and negatively affected indigo bunting nesting success [6], but edge did not depress Acadian flycatcher nest survival [7]. In investigations of