BREEDING BIRD RESPONSE TO FIELD BORDER PRESENCE AND WIDTH

Avian communities can benefit from reconstructed herbaceous, strip habitats among agriculture; however, any benefits may be limited by width-dependent factors such as edge effects. We used 2 years of strip-transect surveys to evaluate avian density, richness, and conservation value between non-, narrow (mean width = 8.2 m), and wide (mean width = 40.7 m) field borders on intensive row-cropped field margins in the agriculture-dominated Mississippi Alluvial Valley. Wide field borders supported two times more birds (7.0 birds/0.2 ha) than narrow borders (3.6 birds/0.2 ha), which supported six times more birds than no border (0.6 birds/0.2 ha). Mean bird species richness was over five times greater in bordered (0.80-1.10 species/0.2 ha) than non-bordered margins (0.14 species/0.2 ha), but was largely uninfluenced by border width. We documented more bird use of agricultural fields and wooded fencerows adjacent to bordered than non-bordered margins. Red-winged Blackbirds (Agelaius phoeniceus) and Dickcissels (Spiza americana) had the strongest positive response to field border presence and width. Wide borders attracted high densities (2.0 birds/0.2 ha) of Dickcissels, an edge-sensitive species, suggesting the conservation potential of herbaceous vegetation patches <50 m of wooded edges for grassland birds. Extensive implementation of field borders, particularly of enhanced width, may contribute substantially to grassland bird conservation strategies in intensive, agricultural landscapes, although confirmation of these benefits requires additional demographic information.