Energetic cost of moult in macaroni penguins (Eudyptes chrysolophus) and rockhopper penguins (E. chrysocome)

Summary

• 1. Energy expenditure of moulting macaroni penguins (Eudyptes chrysolophus) and rockhopper penguins (E. chrysocome) was measured using oxygen consumption as an index of metabolic rate.

• 2. Total energy expenditure decreased throughout moult from 1,952 to 1,102 kJ day⁻¹ for macaroni penguins, and from 1,390 to 722 kJ day⁻¹ for rockhopper penguins, during which time the body mass of the fasting birds also decreased by 46 and 43%, respectively.

• 3. During feather loss mass specific energy expenditure peaked at 386 kJ kg⁻¹ day⁻¹ in macaroni penguins and 379 kJ kg⁻¹ day⁻¹ in rockhopper penguins.

• 4. Energy expenditure estimated from mass loss was 32 and 27 % higher for macaroni and rockhopper penguins, respectively, than that estimated from oxygen consumption. Possible reasons for this are discussed.