Mattson, B.J. 2001. Relationships between multi-scale habitat features and breeding biology of ovenbirds and hermit thrushes. M.S. Thesis, University of Minnesota. 79 pp.
Many Neotropical migratory songbirds breeding in temperate forests have declined across their geographic ranges. Populations breeding in large, contiguous forests like those in boreal and northern hardwood forests may support populations breeding in fragmented hardwood forests of the central United States. If this is correct, then regional declines may exacerbate continental declines. In northern Minnesota and northern Wisconsin, northern hardwoods are being modified by silvicultural, agricultural and other anthropogenic practices. These changes may explain recent rises in nest predators that favor human-dominated landscapes and regional declines in several ground-nesting songbirds. To address this problem, I assessed effects of habitat characteristics at multiple scales on the breeding biology of two ground-nesting songbirds in mature northern hardwood stands. During summer of 2000, I located and monitored 88 ground nests of songbirds in Aitkin County, Minnesota. In addition, I tracked 219 Ovenbird (Seiurus aurocapillus) territories to determine densities, pairing success, and fledging success. At the microsite scale, only fern cover consistently predicted nest predation for both all ground nesters and Ovenbirds. A substrate with shallow leaf litter and few ferns surrounded by a microsite with higher fern cover was associated with depredated Ovenbird nests. At the patch scale, Ovenbird nest predation was higher away from clearcuts. Using different radii around plot centers, both ground nest survival rates and Ovenbird fecundity 1) increased as forest patch size increased within 3-3.5 km, and 2) decreased as forest edge increased within 1.25-1.5 km. No particular edge type within 1.25 km of plot centers could explain the variation in nesting success or fecundity. Based on these results, I suggest that ground nest predation may be high in areas with shallow leaf litter, high fern cover, small forest patches, and high forest edge density. Evaluating how nesting success varies with habitat characteristics at multiple scales is critical for assessing potential effects of forest management on songbirds in northern hardwoods.