Abstract

Physiologists have made few studies on hummingbirds despite the attention that these birds deserve because of their small size and their ability to fly in a small con- tainer. By measuring oxygen consumption I have been able to calculate their rate of metabolism at rest and in flight and their energy needs over a 24-hour period. It has also been possible to measure the depth of the torpidity that some investigators have suspected occurs and to make a rough estimate of the non-stop flight range of hum- mingbirds. METHODS Five Anna (Calypte anna) and two Allen (Selasphorus sasin sas were studied. These were captured as nestlings or as adults and wer ture of water, sugar, milk, and Mellon's food, or a mixture of wat strained liver. Rate of metabolism was measured by oxygen con circuit volumetric apparatus similar to that described by Morrison minations during which no flying was wanted, the animal chamber 5 inches in diameter and 3 inches high (inside measurements). For d ing which the bird was expected to fly, a bell jar 6 inches in diamete was used. Suitable surfaces of soda lime and calcium chloride we and the large bell jar was equipped with a fan to stir up the air and tion of carbon dioxide and water vapor. These chambers were conne of oxygen and when in use were submerged in a water bath to keep inside them constant. Food was provided for the birds in the bell j special cases. When a bird was confined in the apparatus for se weighed both before and after, and the weight used for calculation at any period during the experiment was arrived at by interpolation ments the animal was weighed only at the end. The oxygen consum this paper are expressed in cubic centimeters of gas at 0OC. and 76 Acknowledgment.-I am much indebted to Mr. and Mrs. Eric plying me with the Allen Hummingbirds used and for much valuab for hummingbirds in captivity.

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