Basal and field metabolic rates of Streaked Shearwater during the chick-rearing period

The energetics of adult Streaked Shearwaters Calonectris leucomelas during the chick-rearing period were examined on Awa Island, Japan, in 2008 and 2009. Basal metabolic rates (BMR) were quantified using an open-flow respirometry system and field metabolic rates (FMR) were quantified using a doubly labelled water (DLW) method. In addition, we used activity loggers to estimate time allocations for different activities at sea. BMR was 0.0124 kJ g(-1) h(-1) (+/- 0.0153, N=4) on average and corresponded to 54% of the value predicted from allometric equations. FMR was 0.0634 kJ g(-1) h(-1) (+/- 0.0331, N=3) and was equivalent to 5.1 times BMR, which was higher than values reported for albatrosses (2-4 times BMR). Shearwaters made 50.3 landings a day (+/- 9.8, N=12) and spent 44.8% (+/- 8.0, N=12) of their time sitting on the water. They landed on water approximately twice as often as albatrosses (which have been well-studied using DLW), but they both spent similar proportions of their time on water. Frequent landings at sea, and frequent takeoffs, may generate incremental energetic expenses because of the use of flapping flight; therefore, the Streaked Shearwater's relatively high FMR may be related to its high number of landings.

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