Comparison of methods for evaluating energy expenditure of incubating wandering albatrosses

Measurements of incubation energetics can vary depending on the method used to measure metabolism of an incubating bird. Therefore, we evaluated the e nergy expenditure of six male and four female wandering albatrosses (Diomed ea exulans Linnaeus) using doubly labeled water (DLW), the rate of mass los s, and estimates of metabolic water production derived from water influx ra te (WIR). Incubation metabolic rates (IMR) determined with DLW (169 +/- 21 kJ kg(-1) d(-1) SD) were significantly lower than estimates derived from ma ss loss (277 +/- 46 kJ kg(-1) d(-1) SD) and WIR (males = 289 +/- 60 kJ kg(- 1) d(-1) vs. females = 400 +/- 69 kJ kg(-1) d(-1) SD). Estimates of IMR fro m mass loss and WIR were similar to IMR (305 +/- 39 kJ kg(-1) d(-1) SD) det ermined by respirometry in a previous study, and IMR from DLW was similar t o estimates based on heart rate(HR;147 +/- 26 kJ kg(-1) d(-1) SD) determine d in another study. Applying the different measurements of IMR to construct an energy budget, we estimate that a breeding pair of wandering albatrosse s spends 124-234 MJ to incubate the egg for 78 d. Finally, IMRs determined with DLW and HR were similar to estimated basal metabolic rates derived fro m six different allometric equations, suggesting that heat production from adult maintenance metabolism is sufficient to incubate the egg.