Edge-related nest predation associated with the retention of residual trees in harvested hardwood stands

Abstract

We examined edge-related predation in June-August 1998 on artificial ground nests associated with the retention of residual trees in harvested oak (Quercus spp.)-hickory (Carya spp.) stands in a state in Pennsylvania. We tested the hypothesis that predation rates on nests did not vary with distance from edge in retention stands and adjacent unharvested forest stands. Artificial nests were placed during five time periods (trials) in three representative retention stands in Rothrock State Forest along random transects at four distances perpendicular to the edge: 50 m into the retention stand, at the edge, 50 m into the adjacent forest, and 150 m into the adjacent forest. Artificial nests consisted of three large brown chicken (Gallus gallus) eggs to simulate nests of Ruffed Grouse (Bonasa umbellus) and Wild Turkey (Meleagris gallopavo). Twenty-three % (82/358) of the nests were disturbed during the five trials combined. Nest fate was not influenced by the distance of nests from the edge (P = 0.88). We also found an interaction between trial and site (P = 0.01); in particular, one site (Cooper's Gap) had much higher predation rates during trials 3-5 when abundances of American Crows (Corvus brachyrhynchos) were higher at the site. Predation rates observed in our study were comparable to those found elsewhere in other harvested forests of Pennsylvania, where the abundance of crows is known to be relatively low. Nest predation rates in retention stands probably did not vary with distance from edge because nests were well concealed by a dense layer of ground-level vegetation regardless of distance from an edge. We hypothesize that variation in predation rates among sites may be explained by differences in the degree of heterogeneity, i.e., extent of edges and amount of habitat contrast, within and among adjoining habitats. We conclude that habitat conditions created by retention stands do not have a major negative effect on the nesting success of common, ground-nesting gallinaceous birds.