ENERGETIC COST OF MOLT IN MACARONI PENGUINS (EUDYPTES-CHRYSOLOPHUS) AND ROCKHOPPER PENGUINS (EUDYPTES-CHRYSOCOME)

Energy expenditure of molting macaroni penguins (E. chrysolophus) and rockhopper penguins (E. chrysocome) was measured using oxygen consumption as an index of metabolic rate. Total energy expenditure decreased throughout molt from 1952 to 1102 kJ day-1 for macaroni penguins, and from 1390 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. 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. 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.