Are Effects of Forest Fragmentation on Avian Nesting Success Mediated by Landscape Composition

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

9904058 Robinson Habitat fragmentation fundamentally affects community structure and trophic interactions. Numerous studies of forest birds support the widely held notion that the fragmentation of breeding habitat significantly decreases annual reproductive success. The mechanisms underlying this effect are generally reported as increased rates of nest predation and brood parasitism. Nonetheless, most studies have focuses on local, patch-specific features of fragmentation such as distance to edge and tract size. Less consideration has been given to the broader landscape outside forest fragments. Indeed, recent evidence suggests that the effects of fragmentation on forest birds change with landscape composition. Interactions between local and landscape processes are poorly understood, but potentially complex because many processes co-vary with the magnitude of forest fragmentation. This study will assess directly how landscape composition affects the outcome of fragmentation on birds nesting in southern Illinois. This region contains over 500,000 ha of forest in landscapes that vary widely in the amount of forest cover and relative coverage of different non-forest cover types (crops versus grassland). This study will first classify habitat type surrounding forest patches. Then, replicate patches will be selected in four different landscapes (high and low fragmentation in grassland or crop matrix) in which studies of reproductive success of songbirds will be measured. Factors affecting song bird reproductive success include brood parasitism, nest predation and alteration of understory vegetation by deer browsing. These factors will then be quantified and related to reproductive success. Results of this study will inform local and regional conservation strategies and will constitute a unique case history of how and why local demographic processes can be conditional upon larger-scale phenomena.