Depredation of Artificial Ground Nests in a Managed, Forested Landscape

Abstract

The effects of forest fragmentation on avian nesting success have been examined experimentally using artificial nests in a number of studies (review by Paton 1994). Yahner and Scott (1988), for example, noted a direct relationship between amount of forest fragmentation created by clearcutting and rates of predation on artificial avian nests; conversely, Yahner et al. (1993) did not observe greater predation rates on artificial nests despite greater fragmentation resulting from additional clearcutting on the same study area. Furthermore, as a direct consequence of forest fragmentation the availability of suitable nest sites declines, perhaps enabling predators more readily to find nests located in the remaining forested tracts (patches or corridors) referred to as the ecological-trap hypothesis (Gates & Gysel 1978). Forest clearcutting for ruffed grouse (Bonasa umbellus) habitat in central Pennsylvania (U.S.A.) provided us with an ideal opportunity to test whether depredation of artificial ground nests differed (1) among those placed in contiguous forest, forested corridors, and forested patches and (2) between those placed at sites used repeatedly (fixed nest sites) versus random nest sites in these three habitats. To our knowledge, predation rates on artificial nests at fixed versus random sites as a function of size and shape of forested tracts have not been examined.