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Field Metabolic Rate And Food Consumption By Free-Living Anna's Hummingbirds (Calypte Anna), Donald R. Powers, Kenneth A. Nagy

Faculty Publications - Department of Biological & Molecular Science

We measured C02 production and water flux using doubly labeled water in wild Anna's hummingbirds living in the Santa Ana Mountains of Southern California during autumn (September) of 1981. The estimated field metabolic rate (FMR) of a hummingbird maintaining a constant body mass (mean 4.48 g) is about 32 kl/day, which is 5.2 times basal metabolic rate (BMR). Metabolic rates during daylight hours were about 6.8 X BMR, less than one-half that expected for an Anna's hummingbird in continuous hovering flight. We estimated nighttime metabolism to be near 2.1 X BMR, which is about what would be expected for a …