Nestling bioenergetics in Magellanic Penguins: Does it really cost more to raise a son?

JAVIER CIANCIO; MELINA BARRIONUEVO; ESTEBAN FRERE

Conferencia; WSTC7; 2021

world seabird union

For dimorphic species,it is assumed that the larger sex is more costly to raise due to a greater energydemand and food consumption. We assessed this hypothesis by: a) comparing differencesin nestlings? growth curves according to sex (146 nestlings-3 study years) andb) comparing parental costs through an individual bioenergetic model based onthe observed growth in mass and the energetic cost of raising a nestling after hatching.The asymptotic mass of males was 11.41% heavier than females, but thedifference in energy requirements was only 2.6% larger. Nestling growth seems to peakbetween days 10-30. Food provided to nestlings constitutes a minor fraction inthe energy budget of adults, for which most of the energy is required forcommuting to foraging areas, diving and thermoregulation. Therefore, the smalldifference between chick sexes does not seems to be a significantly extra costfor parents to raise a male.