Nest success of grassland sparrows on reclaimed surface mines
Grasslands resulting from surface mine reclamation support grassland songbird populations in several midwestern and eastern states in the United States, especially where reclaimed mines are large (>1,000ha). However, most reclaimed surface mines in Pennsylvania are small (<200ha), and nest success is unknown. We evaluated nest success of grasshopper (Ammodramus savannarum), Henslow's (A. henslowii), and Savannah sparrows (Passerculus sandwichensis) on 4 reclaimed surface mines (50-180ha) in western Pennsylvania, USA from 2006 to 2007. Overall nest success based on mean covariate values was 0.435 (95% CI = 0.376-0.504) for grasshopper sparrows, 0.396 (95% CI = 0.295-0.533) for Henslow's sparrows, and 0.158 (95% CI = 0.063-0.392) for Savannah sparrows. These estimates of nest success are comparable to those on larger reclaimed mines and other habitats. Grasshopper and Henslow's sparrow nests that were well concealed were less likely to fail than highly visible nests (??visible = -0.028, CI = -0.051 to -0.005 for grasshopper sparrows; ??visible = -0.063, CI = -0.112 to -0.014 for Henslow's sparrows), and nests in areas with surrounding deep litter were more likely to fail than nests in areas with shallow litter (??litterD = -0.145, CI = -0.335 to 0.045 for grasshopper sparrows; ??litterD = -0.676, CI = -1.187 to -0.116 for Henslow's sparrows). Savannah sparrow nests in areas with high visual obstruction by vegetation were less likely to fail than nests in areas with sparse and short vegetation (??VisOb = 0.048, CI = 0.006-0.091). Daily probability of survival for grasshopper sparrow nests was greatest early and late in the breeding season, and Savannah sparrow nest survival followed a decreasing linear trend. Nest survival of Henslow's sparrows was greater on warm days (??temp = 0.197, CI = 0.014-0.379), whereas for Savannah sparrows nest survival decreased on warm days and on days with rain, but for Savannah sparrows confidence intervals of weather effects included zero (??temp = -0.098, CI = -0.246 to 0.050; ??rain = 3.13, CI = -14.19 to 20.45). We suggest that small reclaimed surface mine grasslands can provide valuable nesting habitat and could be important to the conservation of grassland bird populations. Because nest success can increase in the latter part of the nesting season, agricultural disturbances or management activities in mid- to late summer could adversely affect reproductive success. ?? 2011 The Wildlife Society.