INDIRECT EFFECTS OF GYPSY-MOTH DEFOLIATION ON NEST PREDATION

Large areas of forested land are altered each year from gypsy moth (Ly mantria dispar) larvae feeding. Little is known about the impacts of f orest defoliation on populations or reproductive success of forest-dwe lling birds. Therefore, we investigated the effects of defoliation by gypsy moth larvae on the vulnerability of artificial bird nests to pre dation. We placed 450 nests along transects in a West Virginia oak-hic kory (Quercus/Carya spp.) forest that had received variable defoliatio n for 3 years. Nests placed in defoliated sites suffered a higher pred ation rate (41.6%) than did those in nondefoliated sites (22.7%, P = 0 .001). Nests placed less-than-or-equal-to 1 m from the ground suffered higher predation than those placed >1 m (46.4 vs. 21.7%, P < 0.001). Probability of predation was not directly related to nest concealment (i.e., percent vegetational cover less-than-or-equal-to 1 m of nests; P = 0.50), percent canopy cover (P = 0.55), or distance (5 vs. 10 vs. 15 m) from transect (P = 0.39). Consideration of effects of defoliatio n on avian habitat and productivity should be an integral part of mana gement plans in forests vulnerable to gypsy moths.