Sexual differences in food provisioning in Magellanic Penguins

FRERE, E., YORIO, P. & CIANCIO, J.

Ciudad del Cabo

Conferencia; 2nd World Seabird Conference; 2015

World Seabird Union

Parental investment is defined as any investment by the parent in an individual offspring thatincreases the offspring's chance of surviving. Food provisioning is one of the strongest traits affectingoffspring Darwinian fitness, and is positively linked with offspring survival in many altricial and semialtricial birds. The overall food provided by a parent depends on its feeding frequency and mealsize. Recent studies on Magellanic penguins demonstrated differences in the foraging behaviourbetween sexes, but quantitative evidence for the differential sexual investment in food provisioningby parents is yet unavailable. Stable isotope values integrate information on feeding rate andamount of food obtained in each feeding bout. We used stable isotopes in blood of 121 chicks andtheir parents to assess the sexual differences in food provisioning at nine colonies along thePatagonian coast (40º-53º S). Given the uncontrolled sources of uncertainty (e.g. discriminationfactor, diet differences among colonies), the heuristic Euclidean distances between the offspring andits parent was used as a proxy of diet similarity. Overall mean chick stable isotope signature wascloser to males (0.11) than to females (0.27) (T-test p < 0.0001). The Magellanic Penguin is a sexuallydimorphic species, and differences in body size could be affecting the bulk and type of food providedby each sex, by either the amount of food carried to the nest or by the differential abilities to exploitthe resources related to a larger body size. In addition, a three way ANOVA with sex, colony, andseason (early or late chick rearing stage) as fixed effects showed only significant effect of sex onEuclidean distances, which suggests that the greater contribution to overall food provisioning bymales would be widespread across the breeding range and seasons.