Habitat-area Relationships of Shrub-scrub Birds in South Carolina

Sensitivity to reductions in habitat area are widely accepted as a factor in the declines of many mature-forest passerines. Although evidence from a number of sources shows significant declines among many Neotropical migratory (NTMB) and temperate migrant (TMR) early-successional birds, little information exists regarding the potential for area-sensitivity in those species. Here we report the results of research on habitat-area considerations of birds in clearcut habitats in some upland forests in South Carolina. Using single, fixed-radius point counts in each clearcut, we measured avian community composition in 21 piedmont clearcuts (0.5-13 ha) and 28 (4-25 ha) mountain clearcuts. Analysis by simple linear regression showed that estimates of richness and relative abundance for NTMBs, edge-interior species and shrub-scrub species varied positively with increasing clearcut size in piedmont sites (P ≤0.05). Community level responses to clearcut area were not statistically significant in mountain sites. Incidence functions describing responses of several species to clearcut size class suggested sensitivity to patch size in piedmont sites but not in mountain sites. Potentially area-sensitive species in the piedmont included the prairie warbler (Dendroica discolor), yellow-breasted chat (Icteria virens), field sparrow (Spizella pusilla), and eastern towhee (Pipilo erythrophthalmus). These results suggest that patch size should be considered in early-successional forest bird conservation.

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