Habitat requirements of Henslow's Sparrows wintering in silvicultural lands of the Gulf Coastal Plain

Abstract

Henslow's Sparrow (Ammodramus henslowii) is one of several grassland bird species that has declined during the last several decades. Although several studies have characterized the habitat requirements of breeding Henslow's Sparrows, winter habitat requirements for the species remain poorly known. The purpose of our study was to identify habitat variables associated with occupancy by Henslow's Sparrow on silvicultural lands in the core of its winter range in the Gulf Coastal Plain. Forty-one study sites were chosen on lands managed for timber production in Baldwin County, Alabama. Henslow's Sparrows selected moist sites that occurred as pitcher plant bogs or as transition areas between wet pitcher plant bogs and drier upland areas. A multiple logistic regression model identified the density of the grass Panicum verrucosum and the density of pitcher plants as the variables best able to explain the presence of Henslow's Sparrows. Sites occupied by Henslow's Sparrows had higher herbaceous vegetation densities and had been disturbed by timber harvest and/or fire more recently than unoccupied sites. Within occupied sites, Henslow's Sparrows chose areas with higher densities of herbaceous vegetation, especially P. verrucosum.