The influence of interspersion on marsh bird abundance in New York

Interspersion is a key habitat component related to marsh bird abundance, but is not easily quantified. We used Fragstats 3.3 and aerial photos to measure interspersion within wetlands as m/ha of interface between vegetation and water (i.e., edge density). We then related edge density and other factors (marsh area, cover-to-water ratios, marsh area within 5 km) to the abundance of marsh birds on 16 emergent wetlands in New York during 2005. Abundance was assessed via call broadcast surveys for American Bittern (Botaurus lentiginosus), Least Bittern (Ixobrychus exilis), Pied-billed Grebe (Podilymbus podiceps), Sora (Porzana carolina), and Virginia Rail (Rallus limicola). Interspersion, as measured by edge density, was the best predictor of abundance for all species but Pied-billed Grebe (r(2) = 0.30-0.7 1). Vegetation and water interspersed in a spatially complex pattern likely increases breeding diversity and density of marsh birds. Modern spatial analysis programs provide opportunities to quantify interspersion without intensive field work or calculations, which can lead to more accurate research and management efforts focused on marsh birds.