Stable isotopic determinations of trophic relationships of great auks.

Stable isotopic ratios of animal tissues are related to those of their foods and can be used in palaeoecological reconstructions, including those of extinct animals. Nitrogen isotopic analyses of marine organisms from coastal Newfoundland and Georges Bank were used to construct a model predicting collagen δ15N values for seabirds feeding at various trophic levels (TL). This model was tested by measuring bone collagen δ15N values of extant alcids from the northwest Atlantic and high Arctic. Isotopic analysis of bone collagen of the extinct great auk (Pinguinus impennis), the last flightless seabird in the northern hemisphere, indicate that this species occupied a trophic continuum from TL3 (crustacean diets) to TL5 (diets of piscivorous fish). We suggest that (a) great auk chicks and juveniles occupied lower trophic levels and probably consumed euphausiids, and (b) great auks fed offspring via regurgitation, as do dovekies (Alle alle), the only extant fully planktivorous alcid in the Atlantic, and unrelated penguins of the southern hemisphere.