Implications of Field Management for Henslow's Sparrow Habitat at Saratoga National Historical Park, New York

Mazur, Rachel

The early successional nature of Henslow's sparrow habitat requires rotational fieldmanagement, but certain types of management preclude occupancy. To determineappropriate management of Henslow's sparrow habitat, components of adequate habitat andthe influence of field management on their development and maintenance were studied atSaratoga National Historical Park, New York. There is growing evidence of a decline of grassland-dependent birds, including the Henslow's sparrow (Ammodramus henslowii), in both northeastern and midwestem North America (Aslcins 1993). Results from the Breeding Bird Survey between 1965 and 1994 show a decline in the Henslow's sparrow population of 8.2% continent-wide, and 12.1% in New York State (Hines et. al 1995). The Henslow's sparrow is currently under review by the U.S. Fish and Wildlife Service for consideration as a candidate for listing as endangered or threatened under the Endangered Species Act (USFWS 1991), and in New York State it is listed as a species of special concern (Andrle and Carroll 1988). Grassland habitat was fragmented with the introduction in the 1950's of row-cropping and alfalfa monocultures. Pesticides, mechanical cropping, mowing during nesting, forest regeneration, and residential and commercial development on farmland are additional threats to breeding grassland-dependent birds (Cody 1985, Andrle and Carroll 1988, Warner 1994). As habitat on the midwestem prairies rapidly disappears, the role of eastern grasslands has increased in importance in sustaining dwindling populations continent-wide (Askins 1993). Any remaining habitat must be maintained through careful management (Aslcins 1993, Smith and Smith 1992). The goal of this research project was to determine components of adequate Henslow's sparrow habitat and the factors most influential in its development. To accomplish this goal, my objectives were to: (1) enumerate and map the population of Henslow's sparrow at SNHP; (2) quantify vegetation characteristics of Henslow's sparrow territories in the spring and post-fledging; and (3) explore factors that affect field occupancy by Henslow's sparrows.