Site selection of Henslow's sparrows wintering on the upper Texas Coast

Abstract

The Henslow's sparrow (Ammodramus henslowii) selects wintering sites that consist of damp areas with tall grasses, standing dead weeds and scattered shrubs. The smallest study site, a grassy opening at W.G. Jones State Forest, was approximately .76 ha. I identified 3 Henslow's sparrows during 2 avian surveys of this small field. Two other sites, with approximately .83 ha, showed similar small area requirements for the wintering Henslow's sparrow. The study sites had other common vegetation features: tall to medium bunch grasses, litter depths, and vegetation heights (forbs and woody plants). The grass structure was common to all the occupied sites. When one of the structural components was missing, either tall grasses, relatively high standing dead vegetation or litter depth, the Henslow's was predictably absent from the field. Each study site also had obligate or facultative wetland plant species and immediate access to trees and shrubs for protective cover. The sites with the highest number of Henslow's sparrows had a high diversity of grass species. Finding and gaining access to the remaining prairie along the upper Gulf Coast is increasingly difficult. Only a few native prairies remain in the region. The significant (-8.8%) population decline of the Henslow's sparrow reflects the habitat loss for many of the grassland species of North America.