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

-The 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. Received 6 March 1981, accepted 9 July 1981. SURFACE mining in West Virginia drastically alters the environment. What may have once been a hardwood forest becomes a field of grasses, forbs, and some woody plants. As habitat complexity is reduced, a major shift in the bird community occurs, and those species that nest on or near the ground and require little if any woody vegetation are attracted to the area. This community includes the Grasshopper Sparrow (Ammodramus savannarum), Savannah Sparrow (Passerculus sandwichensis), Vesper Sparrow (Pooecetes gramineus), Horned Lark (Eremophilia alpestris), Eastern Meadowlark (Sturnella magna), and Killdeer (Charadrius vociferus). As woody vegetation invades the area, Field Sparrows (Spizella pusilla) and Indigo Buntings (Passerina cyanea) may initiate nesting activities. Although these grasslands are quite different 1 Published with the approval of the Director, West Virginia Agricultural and Forestry Experiment Station, as scientific article number 1702. from the habitats where true grassland sparrows evolved, these species are now using this new land resource (Whitmore and Hall 1978). Whether or not the sparrows are actually benefiting from this new habitat is unknown. Accordingly, we studied the breeding biology of the sparrow species nesting on a reclaimed surface mine in northern West Virginia. STUDY AREA AND METHODS A 41.5-ha reclaimed surface mine (Great Mine), located 1 km south of Valley Point, West Virginia (39'34' and 79038') at an elevation of 580 m, was chosen for this study. This site was stripped for coal three times before final reclamation in 1974. The gently rolling topography is dominated by tall fescue (Festuca arundinacea), with some serecia lespedeza (Lespedeza cuneata), blackberries (Rubus spp.), many invading herbaceous species, and scattered black locust (Robinia pseudoacacia) and autumn olive (Eleagnus umbellata). The site also has bare areas due to highly acidic materials and very rocky soils and is surrounded by woodlots and pastureland. Data were collected during three successive breed157 The Auk 99: 157-164. January 1982 This content downloaded from 157.55. 39.49 on Mon, 29 Aug 2016 04:26:23 UTC All use subject to http://about.jstor. org/terms 158 WRAY, STRAIT, AND WHITMORE [Auk, Vol. 99 TABLE 1. Mean clutch size for four sparrow species, 1978-1980. Year Vesper Sparrow Grasshopper Sparrow Savannah Sparrow Field Sparrow 1978 3.8 ? 0.4 (20)a 4.5 ? 0.6 (16) 3.9 ? 0.7 (14) 1979 3.9 ? 0.5 (22) 4.5 ? 0.5 (15) 4.1 ? 0.8 (12) 3.4 ? 0.5 (5) 1980 3.5 ? 0.6 (21) 4.1 ? 0.8 (13) 4.2 ? 0.6 (10) 3.8 ? 0.4 (18)