EDGE- AND AREA-SENSITIVITY OF SHRUBLAND BIRDS

Populations of shrubland birds in eastern North America have consistently declined since the 1960s, but conservation is hampered by an inadequate understanding of the area requirements of most species. We examined the sensitivity of shrubland specialists to (a) the area of shrub stands and (b) proximity to mature-forest edges, and we evaluated whether habitat characteristics, food resources, or productivity of bird populations could have caused the relationships we identified. In 2002–2003, we used constant-effort mist-netting on 6 small (4–8 ha) and 6 large (13–16 ha) regenerating clearcuts that were 4–6 years post-harvest in southern Ohio, USA. We placed 3 nets at 20, 50, and 80 m from the mature-forest edge (n = 9 nets per site), and we sampled vegetation, fruit, and arthropods at each net. Seven of 8 shrubland specialists, particularly blue-winged warbler, prairie warbler, yellow-breasted chat, indigo bunting, and field sparrow, avoided mature-forest edges, with twice as many birds caught 80 m from edges compared to 20 m. Abundances of most species, especially yellow-breasted chats, were positively correlated with area, though the combined area effect was not statistically significant. We found no evidence of reduced avian productivity in small stands. Neither area nor edge was associated with habitat characteristics, fruit abundance, or arthropod biomass. Our results suggest shrubland birds avoid habitat edges. Thus, small or narrow cuts may not provide optimal habitat for this suite of declining species, and managers should consider options to minimize edge and provide larger patches of shrubland habitats in landscape-scale planning efforts.