Isotopic Discrimination in the Double-Crested Cormorant (Phalacrocorax auritus)

PLoS One. 2015 Oct 16;10(10):e0140946. doi: 10.1371/journal.pone.0140946. eCollection 2015.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Birds / metabolism*
  • Carbon Isotopes / pharmacokinetics
  • Carbon Isotopes / pharmacology
  • Feeding Behavior / physiology*
  • Food Preferences / physiology*
  • Nitrogen Isotopes / pharmacokinetics
  • Nitrogen Isotopes / pharmacology
  • Organ Specificity / physiology
  • Sulfur Isotopes / pharmacokinetics
  • Sulfur Isotopes / pharmacology


  • Carbon Isotopes
  • Nitrogen Isotopes
  • Sulfur Isotopes

Grants and funding

This work was funded by the United States Department of Agriculture, Wildlife Services, National Wildlife Research Center, MS Field Station (!ut/p/a0/04_Sj9CPykssy0xPLMnMz0vMAfGjzOK9_D2MDJ0MjDzd3V2dDDz93HwCzL29jAwMTfQLsh0VAXWczqE!/). Funding was received by PDC and ECC (Grant #62383). These funders participated in study design, data collection, decision to publish, and preparation of the manuscript; and provided facilities, staff, and funding to support capture and care of cormorants for this study. This work was also funded by Berryman Institute ( Funding was received by ECC. These funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.