Reproductive Success of Grassland Sparrows on a Reclaimed Surface Mine in West Virginia

Abstract

AbstractThe reproductive success of Grasshopper Sparrows (Ammodramus savannarum), Savannah Sparrows (Passerculus sandwichensis), Vesper Sparrows (Pooecetes gramineus), and Field Sparrows (Spizella pusilla) breeding on a reclaimed surface mine in northern West Virginia was studied from 1978 through 1980. Only Vesper Sparrows showed significant (P < 0.05) annual differences in clutch size. Predation was the major cause of egg and nestling losses during all 3 yr. Of 185 nests located, 80 (43%) were presumed lost to predators. Our study site, surrounded by woodlots and pastureland, apparently concentrated predators. We believe northern black racers (Coluber constrictor constrictor) and Common Crows (Corvus brachyrhynchos) were the major predators. Generally, predators were equally successful in locating nests during the incubation and nestling periods. Variable nesting success, calculated from exposure for the species during the 3 yr, reflects differential predation pressure. Productivity estimates suggest that adults are not replacing themselves and immigration is necessary to maintain a stable population. Apparently, environmental cues are sufficient to elicit a settling response, but, due to predation, reproductive success is low. Although surface mining is providing new nesting habitat for these species, the inadequate reproductive success experienced on our site suggests that these manmade grasslands may not be of benefit to the sparrow populations in this area. Breeding densities during the 3 yr were variable and may reflect poor breeding success, changes in the vegetation, availability of more suitable nesting habitat, and differential mortality during migration and on the wintering grounds.