title: Isotopic Discrimination in the Double-Crested Cormorant (Phalacrocorax auritus).
abstract: The diet-tissue discrimination factor is the amount by which a consumer's tissue varies isotopically from its diet, and is therefore a key element in models that use stable isotopes to estimate diet composition. In this study we measured discrimination factors in blood (whole blood, red blood cells and plasma), liver, muscle and feathers of Double-crested Cormorants (Phalacrocorax auritus) for stable isotope ratios of carbon, nitrogen and sulfur. Cormorants exhibited discrimination factors that differed significantly among tissue types (for carbon and nitrogen), and differed substantially (in the context of the isotopic variation among relevant prey species) from those observed in congeneric species. The Double-crested Cormorant has undergone rapid population expansion throughout much of its historic range over the past three decades, leading to both real and perceived conflicts with fisheries throughout North America, and this study provides an essential link for the use of stable isotope analysis in researching foraging ecology, diet, and resource use of this widespread and controversial species.
authors.affiliation: Field of Zoology and Wildlife Conservation, Cornell University, Ithaca, New York, United States of America.
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Craig
authors.affiliation: United States Department of Agriculture, Wildlife Services, National Wildlife Research Center, Mississippi Field Station, Mississippi State, Mississippi, United States of America.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Dorr
authors.affiliation: United States Department of Agriculture, Wildlife Services, National Wildlife Research Center, Mississippi Field Station, Mississippi State, Mississippi, United States of America.
authors.forename: Katie C
authors.initials: KC
authors.lastname: Hanson-Dorr
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, United States of America.
authors.forename: Jed P
authors.initials: JP
authors.lastname: Sparks
authors.affiliation: Department of Natural Resources, Cornell University, Ithaca, New York, United States of America.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Curtis
mesh_terms: D000818:Animals; D001717:Birds / Q000378:metabolism*; D002247:Carbon Isotopes / Q000493:pharmacokinetics / Q000494:pharmacology; D005247:Feeding Behavior / Q000502:physiology*; D005518:Food Preferences / Q000502:physiology*; D009587:Nitrogen Isotopes / Q000493:pharmacokinetics / Q000494:pharmacology; D009928:Organ Specificity / Q000502:physiology; D013460:Sulfur Isotopes / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D013460:Sulfur Isotopes