Scientists have long thought that the giant hummingbird (Patagona gigas) was just about as big as a hummingbird could get. They're nearly twice the size of the next largest species, and it was assumed that the energy needed for hovering flight would take the giants close to the upper metabolic limits for an animal that size.
Not so, according to a study led by María José Fernández of the University of California, Berkeley, and the Pontificia Universidad Católica de Chile. Fernández and her colleagues measured the amount of energy burned by giant hummingbirds when hovering and at rest. They also assessed the total amount of energy that the birds use in a day.
The research found that giant hummingbirds do use more energy for their body size than smaller hummingbirds do, but they were still well below what is thought to be the upper metabolic limit. The finding suggests that metabolism is not necessarily the constraining factor in the evolution of hummingbird body size.
The research is published in the May/June 2011 issue of the journal Physiological and Biochemical Zoology.
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