Energy requirements of female macaroni penguins breeding at South Georgia

1. Breeding female Macaroni Penguins (Eudyptes chrysolophus ) were implanted with heart rate, temperature and depth data loggers in order to estimate their rate of energy expenditure from heart rate. 2. The estimated average daily metabolic rates (ADMR) of birds during the brood and creche phases of the breeding season were 8.17 +/- 0.44 W kg(-1) and 8.24 +/- 0.41 W kg(-1) , respectively. There was no significant difference between these estimates and the pooled ADMR for all birds was 8.22 +/- 0.38 W kg(-1) . 3. Metabolic rate while the penguins were at-sea was 9.03 +/- 0.39 W kg(-1) and this was significantly greater than the metabolic rate of 6.27 +/- 0.38 W kg(-1) while they were on-shore. 4. Females undertook shorter foraging trips during the creche phase than during the brood phase. 5. When considered as a breeding pair, Macaroni Penguins expend more energy in raising their chick during the creche phase of the breeding season as the male assists in provisioning the chick only at this time.