Pelagic or benthic prey? Combining trophic analyses to infer the diet of a breeding South American seabird, the Red-legged Cormorant (Phalacrocorax gaimardi)

MORGENTHALER, A., MILLONES, A., GANDINI, P. & FRERE, E.

EMU

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2016 vol. 116 p. 360 - 369

0158-4197

The available information about the feeding habits and preferences of the Red-legged Cormorant(Phalacrocorax gaimardi) generally suggests that this near-threatened South American cormorant is a sedentary benthicforager that also incorporates pelagic prey in its diet. In order to describe the dietary composition and assess the importanceof certain prey types (pelagic vs benthic), we studied the diet of this cormorant on the Argentine Atlantic coast during fourbreeding seasons, using a combined technique of conventional diet assessment (pellets) and stable isotope analysis. Ourresults show that the Red-legged Cormorant forages mainly on pelagic and demersal?pelagic prey. Results of bothtechniques showed the main prey to be the Patagonian Sprat, a small high-energy-content pelagic forage fish, and thePatagonian Squid, a low-energy-content demersal?pelagic invertebrate. We also found an overall low prey diversity andimportant interannual variation for the main prey types, as well as variation between the different breeding stages. Thisstudy therefore contributes new and unambiguous information about the Red-legged Cormorant?s use of trophicresources and suggests that the combination of a conventional technique with stable isotope analysis provides a solidframework for this seabird diet assessment.