Differential parental food provisioning in Magellanic Penguin.

JAVIER CIANCIO; PABLO YORIO; ESTEBAN FRERE

Cape twon

Conferencia; World Seabird Conference; 2015

World Seabird Union and The African Seabird Group

Parentalinvestment is defined as any investment by the parent in an individualoffspring that increases the offspring?s chance of surviving. Food provisioningis one of the strongest traits to affect offspring Darwinian fitness, and ispositively linked with offspring survival in many altricial and semialtricialbirds. The overall food provided by a parent depends on its feeding frequencyand meal size. In sexually dimorphic species, differences in body size couldaffect the bulk and type of food provided by sex, by either the amount of foodcarried to the nest or by the differential skills to exploit the resourcesrelated to a larger body size. The Magellanic Penguin is a semialtricial,sexually dimorphic species. Recent studies demonstrated differences in theforaging behaviour between sexes, but quantitative evidence for thedifferential sexual investment by parent is not available. Stable isotope valuesintegrate feeding rate and bulk of food. We used stable isotopes in blood of chicksand their parents (121 pairs) to assess the differences of food provisioningbetween sexes in nine colonies along the Patagonian Coast.Considering the not controlled sources of uncertainty (e.g. discriminationfactor, different diet across colonies) the heuristic Euclidean distances betweenoffspring and its parent was used as a proxy of diet similarity. Overall mean chickstable isotope signature is closer to males (0.11) than to females (0.27) (Ttestp < 0.0001). A three way ANOVA with sex, colony, and season as fixed effectsshowed only significant effect of sex on the Euclidean distances, which suggeststhe differential role of males would be widespread across the breeding rangeand season.