Growth and energy expenditure of Wandering Albatross Diomedea exulans chicks

Wandering Albatross Diomedea exulans chicks require 9–10 months to achieve adult body size at fledging, at which time they are also sexually size dimorphic. Because the developmental period spans the winter season, chicks must endure severe winter conditions and variability in provisioning effort by their parents. Thus chicks may adjust their rate of energy utilization to accommodate variations in provisioning, but this has not previously been studied. We followed longitudinally the changes in growth, body composition and oxygen consumption of 10 chicks from the end of the brooding period until fledging on the Crozet Islands. Body mass, culmen length and wing length were measured every 10 days and total body water (TBW) and resting metabolic rate (RMR) were measured monthly. Overall growth followed a logistic curve for all chicks, and sexual dimorphism in body mass appeared as early as the second month of measurements (males being heavier than females). Absolute TBW followed a logistic increase like that of body mass and was significantly higher in males owing to the difference in body mass. Conversely, mass-specific TBW (i.e. the proportion of body mass made up of water) did not differ significantly between male and female chicks. Absolute RMR peaked at 1.5 × adult basal metabolism in midwinter when chicks achieved maximum body mass, but decreased to adult levels by the time chicks fledged. The decrease in absolute RMR following attainment of peak mass is atypical of most seabird chicks (Procellariiformes) and may be explained partly by a reduction in size of the gut when parents reduce provisioning effort. The changes in mass-specific RMR did not differ between sexes but male chicks, being heavier, had higher absolute oxygen consumption and therefore greater energy requirements.