BIRD COMMUNITY RESPONSE TO CONSERVATION RESERVE PROGRAM HABITAT IN MARYLAND

Abstract

The populations of many bird species in the United States that use early-successional habitats have been substantially declining over the last 40 years. The main reason for these declines is habitat loss. Land enrolled in the U.S. Department of Agriculture's Conservation Reserve Program (CRP) often represents the only uncultivated herbaceous areas on farmland in the mid-Atlantic and therefore may be important habitat for early-successional bird species. CRP filter strips are strips of herbaceous vegetation that are planted along agricultural field margins and are usually planted with native warm-season grasses or introduced cool-season grasses. We studied the breeding and wintering bird use of CRP filter strips adjacent to wooded edges in Maryland from 2004-2007. We conducted bird and vegetation surveys in filter strips and measured landscape attributes around CRP plantings. We used 5 bird community metrics (total bird density, species richness, scrub-shrub bird density, grassland bird density, and total avian conservation value), species-specific densities and abundances, nest densities, and nest survival estimates to assess the habitat value of filter strips for birds. Bird community metrics were greater in filter strips than in field margins without filter strips, but did not differ between cool-season and warm-season grass filter strips. Most breeding bird community metrics were negatively related to the percent cover of orchardgrass (Dactylis glomerata). Several grassland birds were more common in wide filter strips (>60 m) compared to narrower filter strips (<30 m). The density of early-successional bird species was greater in filter strips with higher plant species richness and shorter and less dense grasses. Wintering bird use was significantly less in filter strips mowed in the fall than in unmowed filter strips. The abundance of northern bobwhite (Colinus virginianus), an important game bird and species of conservation concern, was positively associated with the percent cover of CRP land in the surrounding landscape. These results suggest that the CRP has created additional habitat for many early-successional bird species, but changes in the planning and management of CRP plantings may improve their habitat value for breeding and wintering birds.