Landscape context influences salt marsh bird diversity and area requirements in New England

We evaluated the contributions of spatial distribution, juxtaposition, and quality of salt marsh habitat to salt marsh breeding birds along the New England coast, USA. We divided the region into two landscapes, Long Island Sound and the Gulf of Maine, based on latitude, geologic and human land use histories, and physical characteristics (tidal amplitude, wave energy). Species richness in both landscapes was at least 20% greater on larger salt marshes. Response to marsh isolation and human development varied regionally, with bird species more sensitive to marsh isolation and road proximity in the more pristine (Gulf of Maine) than altered (Long Island Sound) region. Relatively little overlap was evident between regions in predictors of occurrence and effects of marsh area on particular species. These results indicate that: (1) salt marsh bird communities show similar associations with habitat area and isolation as do forest, grassland, and freshwater wetland bird communities, and (2) landscape context mediates the influence of these parameters on the avian community and should be considered when defining the habitat requirements of salt marsh breeding birds.