PREDATION OF ARTIFICIAL NESTS IN HARDWOOD FRAGMENTS ENCLOSED BY PINE AND AGRICULTURAL HABITATS

Nesting success of songbirds often is poor in edge-dominated habitats. Because the spatial juxtaposition of forest fragments relative to oth er habitats may influence nest success, we tested the hypothesis that the depredation rate for bird nests in small hardwood forests mould de crease if the degree of edge contrast with adjoining habitats was redu ced. Over 4 trials, we placed 672 artificial nests (336 each at shrub and ground levels divided equally between edge and interior locations) in small (range = 0.5-5.0 ha) hardwood forest stands enclosed by eith er agricultural fields (n = 7) or mature pine forest (n = 7). Nest pre dation was greater (P = 0.001) in field-enclosed stands (35%) than in pine-enclosed stands (20%) because of greater (P = 0.03) predation of shrub nests. No differences (P > 0.05) in predation rates were detecte d between stand types for ground nests or between strata (i.e., ground nests vs, shrub nests) within field-enclosed stands. Predation rates did not differ (P > 0.05) between edge and interior nests between or w ithin stand types. Nest predation by avian species was not suspected i n pine-enclosed stands (0%), but 18% of the nests depredated in agricu lture-enclosed stands was attributed to birds. The low edge contrast a ssociated with pine-enclosed stands appeared to attract fewer nest pre dators, especially those that preyed on shrub nests. However, the valu e of lower predation rates for shrub nests in pine-enclosed stands may be offset by the presence of fewer shrub-nesting sites relative to si milar-sized field-enclosed stands, because understory development was impoverished, probably as a result of reduced sunlight penetration.