Energy Costs of Incubation and Moult in Petrels and Penguins

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Abstract
Most penguins and petrels fast during lengthy incubation shifts; all penguins fast through their molt. The resulting weight losses can be used to calculate energy costs of these activities and to examine relationships between body weight and energy consumption. Field data for 13 spp. of petrel (albatrosses to storm petrels) and 14 (of 17) spp. of penguin are reviewed and O2 consumption data for 7 penguins are summarized. For incubating and molting birds the log-log relationships between energy consumption (kcal day-1) and body weight have slopes of 0.67-0.77, close to that of non-passerines generally (0.73). The slope for O2 consumption data (0.74) is similar. These data also support the present assumption that only about 1/2 the material lost during these fasts is fat, the rest being mainly water. Proportionate weight loss (g g-1 day-1) during fasting is approximately proportional to body weight (g) to the power of -0.27, as can be predicted theoretically. The daily energy cost of incubation in petrels and penguins is about 1.3-1.4 times the estimated cost of basal metabolism. Daily molt cost in penguins is about twice basal metabolism.