Daily Energy Expenditure of Chick-Rearing Rhinoceros Auklets Cerorhinca monocerata

Chick rearing is one of the most energy-expensive phases of the breeding cycle for adult birds. It has been suggested that the daily energy expenditure (DEE) that birds may sustain over extended time periods may be set at approximately 4×basal metabolic rate (BMR). Parent birds can be expected to face the upper limit of DEE during the chick-rearing period. To determine whether parents rearing chicks exceed the sustainable limits of DEE in the temperate regions, in this study we measured parental DEE of Rhinoceros Auklet Cerorhinca monocerata using the doubly-labeled water method in 2018 and 2019 on Teuri Island, Japan. We found that, with only on exception, all individuals had DEE below 4×BMR. Our findings suggest that Rhinoceros Auklets basically have DEEs within “the maximum sustained working level”.