NESTING SUCCESS OF A DISTURBANCE-DEPENDENT SONGBIRD ON DIFFERENT KINDS OF EDGES

We compared the nesting success of a disturbance-dependent species, th e Indigo Bunting (Passerina cyanea), on different kinds of habitat edg es in five sites (225 total nests) in southern Illinois from 1989 to 1 993. Nest predation rates along agricultural and abrupt, permanent edg es (e.g., wildlife openings, campgrounds) were nearly twice as high as rates along more gradual edges where plant succession was allowed to occur (e.g., treefalls, streamsides, gaps created by selective logging ). Levels of brood parasitism by Brown-beaded Cowbirds (Molothrus ater ) varied significantly among sites and years, but not among edge types . Clutch sizes, however, were significantly smaller at agricultural ed ges where nest predation rates were also high, which suggests either d ecreased food availability or a population dominated by younger and/or lower-quality (poor condition) birds. The results of this study illus trate the need to reevaluate management practices (e.g., wildlife open ings) that are designed to promote populations of disturbance-dependen t wildlife.