Using referential values of δ¹³C and δ¹⁵N to infer the foraging ecology of galápagos seabirds

The Galápagos Penguin Spheniscus mendiculus, Flightless Cormorant Phalacrocorax harrisi, and Waved Albatross Phoebastria irrorata are endemic to Islas Galápagos. They are known to feed on different prey (including crustaceans, cephalopods, and/or several species of epipelagic and benthic fish), in accordance with different foraging strategies. In this work, we used stable-isotope analysis of carbon and nitrogen to corroborate available information on habitat use (δ¹³C) and trophic position (δ¹⁵N). Feather samples from the three species were collected in six different areas prior to the 2011 and 2012 breeding seasons. Results showed differences in foraging strategies between Galápagos Penguins and the other two species (δ¹³C and δ¹⁵N, P < 0.01). The Flightless Cormorant and Waved Albatross showed similar proportions of δ¹³C (P = 0.07), but they occupied different trophic levels (δ¹⁵N, P < 0.01). Isotopic signatures in Galápagos Penguins reflected differences based on their breeding areas (δ¹³C and δ¹⁵N, P < 0.01), which were subject to different environmental conditions. This information could be used to evaluate future ecological conditions among the feeding areas of these species.