Parental investment in Magellanic Penguin eggs and its effect on nestling?s stage

BARRIONUEVO, M. & FRERE E.

EMU

CSIRO PUBLISHING

Año: 2014 vol. 114 p. 259 - 267

0158-4197

Life-history variables evolve in response to cost?benefit trade-offs. For birds, larger eggs are thought to bebeneficial for development of offspring but are energetically costly to produce. Further, egg-size dimorphism within orbetween clutches can vary with proximate and ultimate causes. We undertook a correlational study to evaluate parentalinvestment in eggs by Magellanic Penguins (Spheniscus magellanicus) andhowit affects the growth and survival of nestlingsin Puerto Deseado, Argentina, over 3 years.Weevaluated the variables that affected egg-volume and yolk-area (using a nondestructivetechnique), and determined the effects of egg-volume and yolk-area on growth and survival of young. Females ingood body-condition laid larger second eggs and, in good years (i.e. years of high reproductive success in the colonies ofthe study area), yolk-area of second eggs was larger than that of first eggs. We found a positive association between eggvolumeand nestling body-size and yolk-area was positively related to nestling survival. Our results suggest that the sizeof eggs within clutches varied with year and female body-condition. Moreover we demonstrate for the first time that yolkareais a strong predictor of nestling survival in Magellanic Penguins.