EDGE EFFECT ON NESTING SUCCESS OF GROUND NESTING BIRDS NEAR REGENERATING CLEARCUTS IN A FOREST-DOMINATED LANDSCAPE

Forest fragmentation has been implicated as a cause of population declines of several Neotropical migrant bird species. Fragmentation increases the amount of habitat edge, and reduced nesting success rates near forest edges are well documented in agricultural landscapes (“edge effects”). However, edge effects in predominantly forested landscapes, particularly those related to timber harvest, are poorly understood. This study examines nesting success of ground nesting birds in relation to clearcut edges in a forest-dominated landscape in north-central Minnesota. A total of 383 nests of seven species of ground nesting birds were found and monitored during 1992–1998. Ovenbird (Seiurus aurocapilus; n = 318) and Hermit Thrush (Catharus guttatus; n = 44) nests composed the majority of the sample. Predation accounted for 94% of all nest failures. Brown-headed Cowbird (Molothrus ater) parasitism was low (1.8% for all ground nests). Using proportional hazards regression, distance to nearest clearcut edge was the best predictor of nest failure. For all ground nests, nesting success was 0.18 at 0–100 m, 0.39 at 101–500 m, and 0.52 at 501–954 m from nearest clearcut edge. Source–sink modeling indicated that distances ≤100 m from clearcut edges were sink habitats for Ovenbirds (i.e. recruitment was lower than survival). These results provide strong evidence of a negative edge effect on ground nests, extending 100 m or more from clearcut edges in a forest-dominated area of north-central Minnesota.