Spatial And Temporal Variation Of Diet Within A Presumed Metapopulation Of Adelie Penguins

We investigated temporal and spatial variability in the diet of chick-provisioning Adelie Penguins (Pygoscelis adeliae) breeding at all colonies within one isolated cluster in the southwestern Ross Sea, Antarctica, 1994-2000. We wished to determine if prey quality explained different population growth and emigration rates among colonies. Diet composition was described both by conventional means (stomach samples) and by analysis of stable isotopes in chick tissues (toenails of individuals killed by skuas [Stercorarius maccormicki]). Diets were similar among the four study colonies compared to the disparity apparent among 14 widely spaced sites around the continent. Calorimetry indicated that fish are more energetically valuable than krill, implying that if diet varied by colony, diet quality could attract recruits and help to explain differential rates of colony growth. However, a multiple-regression analysis indicated that diet varied as a function of year, time within the year, and percent of foraging area covered by sea ice, but not by colony location. Stable isotopes revealed similarity of diet at one colony where conventional sampling was not possible. We confirmed that sea ice importantly affects diet composition of this species in neritic waters, and found that (1) quality of summer diet cannot explain different population growth rates among colonies, and (2) stable isotope analysis of chick tissues (toenails) is a useful tool to synoptically describe diet in this species over a large area.Original Abstract: Investigamos la variabilidad temporal y espacial en la dieta de Pygoscelis adeliae que se encontraban aprovisionando a sus polluelos en todas las colonias dentro de un grupo aislado en el mar de Ross sud-occidental, Antartica, entre 1994 y 2000. Deseabamos determinar si la calidad de la presa explicaba las diferentes tasas de crecimiento poblacional y emigracion entre colonias. La composicion de la dieta fue descrita por medios convencionales (muestras estomacales) y por el analisis de isotopos estables en tejidos de los polluelos (unas de las patas de los individuos matados por Stercorarius maccormicki). Las dietas fueron similares entre las 4 colonias estudiadas en relacion a la disparidad de la dieta evidente entre 14 sitios dispersos a traves del continente. Las analisis de calorimetria indicaron que los peces tienen un mayor valor energetico que el krill, sugiriendo que si la dieta varia entre colonias, la calidad de la dieta podria atraer a