Identifying Important Foraging Habitat for Colonial Waterbirds in an Urban Estuary: a Stable Isotope Approach

Abstract

Abstract. Foraging habitat use by colonial waterbirds breeding in New York Harbor was examined to identify resources that were particularly important for the provisioning of young. Stable isotope values of carbon, nitrogen, and sulfur were measured in nestling waterbird feathers to determine the habitat type (ranging from marine to freshwater and anthropogenic) in which adults primarily foraged. Six species were investigated: Black-crowned Night-Herons (Nycticorax nycticorax), Great Egrets (Ardea alba), Glossy Ibises (Plegadis falcinellus), Double-crested Cormorants (Phalacrocorax auritus), Great Black-backed Gulls (Larus marinus), and Herring Gulls (L. argentatus). Waterbird populations exhibited both inter- and intra-specific variation in stable isotope values (P < 0.001), indicating variation in foraging habitat use among focal species across the estuary. Therefore, depending on the species-and region-specific conservation goal, management strategies would potentially need to target very different fora...