Undisturbed breeding penguins as indicators of changes in marine resources

Abstract

Sea-birds fast when breeding ashore and, therefore, breeding success largely depends upon body fuels accumulated at sea and food stored in the stomach for chicks. By weighing breeding king penguins Aptenodytes patagonicus, the authors demonstrate seasonal differences in the daily gain in body mass and duration of foraging trips of breeders at sea. It takes longer for the breeders to obtain food when marine resources are decreasing. The overall gain in body mass of the birds at sea is unchanged. However, they accumulate larger body fuel reserves, which therefore increases their energetic safety margin at predictable times of lower food availability but reduces food brought back to the chicks. Variations in the duration of sojourns into the colony, when penguins come independently to feed the chicks, can be attributed to the stages of the breeding cycle. -from Authors