Nest predation in aspen woodlots in an agricultural area in Alberta : The enemy from within

摘要: Several studies have documented elevated rates of nest predation for passer- ines and grouse in small forest patches near anthropogenic edges. We examined patterns on artificial nests aspen (Populus tremuloides) woodlots fencerows sur- rounded by agricultural land Alberta. Nests were intended to mimic those ground- nesting shrub-nesting passerines. evaluated the relative importance factors at site, patch, landscape risk different predators. Total highest fencerows. Among woodlots, did not differ with woodlot area except 1992, when ground was higher large woodlots. Most shrub depredated birds (corvids House Wrens (Troglodytes aedon)). Corvid smaller closest edge. Predation mammals larger closer farms showed no edge effect. Wren vary any feature, cover, or distance suggest that corvids forage mainly edges can fully penetrate Small are present all but avian pred- ators take eggs before they detected mammals. Nest living within such as wrens mammals, may be equally more important than outside determining nest-predation