Energy Expenditure of Free-Ranging Wandering Albatrosses Diomedea exulans

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Abstract
We measured carbon dioxide (CO₂) production and water influx rates of free-ranging, foraging, wandering albatrosses (Diomedea exulans) attending chicks, by means of doubly labeled water. CO₂ production for nine birds averaged 0.656 ± 0.079 ml CO₂ g⁻¹ h⁻¹. This is equivalent to an overall energy expenditure of 3,354 kJ bird⁻¹ day⁻¹ or 1.83 times measured basal metabolic rate (BMR). This is the lowest field metabolic rate recorded for free-ranging birds and is attributable to the relatively low cost of the soaring flight used by wandering albatrosses as opposed to flapping flight. Energy cost of flight was estimated to be 2.35 times measured BMR. Breeding male and female albatrosses, respectively, spend 77% and 85% of their overall time budget and 83% and 89% of their overall energy budget foraging at sea. The advantage in having an energy-efficient mode of locomotion while foraging is evident. Water influx rates for 14 birds averaged 174 ml kg⁻¹ day⁻¹, of which 57% could be accounted for by water in the food required by the adults alone. The remaining 43% is probably due to the additional food fed to nestlings, along with possible consumption of seawater. Annual food requirement of the population of wandering albatrosses (2,200-2,600 breeding pairs) at the Prince Edward Islands is ~1.69 x 10⁶ kg, comprising 1.35 x 10⁶ kg of squid, 0.17 x 10⁶ kg of fish, and 0.17 x 10⁶ kg of crustaceans and carrion.