Nesting success of a neotropical migrant in a multiple-use, forested landscape

We studied the nesting success of an individually marked population of Kent ucky Warblers (Oporornis formosus), a species that nests in disturbed and u ndisturbed forests, in a heterogeneous, managed forest site in the Shawnee National Forest in southern Illinois from 1992 to 1995. We examined the eff ects of forest stand type (clearcuts of various ages, tree plantations, and older forest) and distance from habitat edges on rates of nest predation a nd brood parasitism by Brown-headed Cowbirds (Molothrus ater). Brood parasi tism levels gradually decreased from 60% to 3% (n = 250 nests) over a dista nce of 2 km from an agricultural edge proximal to a known cowbird foraging site (a pig feedlot), but they did not vary with distance from any other ki nds of edges or with forest stand type. Rates of nest predation (n = 278 ne sts) did not vary with distance from any edges, but they were significantly lower in older forest than within even-aged clearcuts, a tree plantation, and in successional vegetation adjacent to a residential facility. These re sults suggest that, even in fragmented landscapes with high overall levels of parasitism and nest predation, management practices within and immediate ly adjacent to forest tracts can affect the nesting success of some species , but not necessarily as a simple function of distance from edge. For the K entucky Warbler, our results suggest that a management strategy that avoids even-age silviculture and leaves core stands of older forest far from cowb ird feeding areas can increase nesting success to levels similar to those m easured in more forested landscapes.