The Combined Effects of Air Temperature, Wind, and Radiation on the Resting Metabolism of Avian Raptors
Date of Award:
Doctor of Philosophy (PhD)
James A. Gessaman
James A. Gessaman
James A. MacMahon
R. M. Holdredge
LeGrande C. Ellis
Russel M. Holdredge
American kestrels, Falco sparverius; red-tailed hawks, Buteo jamaicensis; and golden eagles, Aguila chrysaetos, were perched in a wind tunnel and subjected to various combinations of air temperature, wind, and radiation. Oxygen consumption was measured under the various combinations of environmental variables, and multiple regression equations were developed to predict resting metabolism as a function of body mass, air temperature, wind speed, and radiation load. Heat transfer analysis of the bird-thermal environment relationship was conducted to produce a biophysical model describing resting metabolism as a function of feather thermal conductance.
Because of differences in surface area to mass ratios and in average feather thicknesses among the three bird species, increases in metabolism due to wind ranged from non-linear in kestrels to linear in eagles. The relationship between wind speed and metabolic increase in red-tails was more linear than in kestrels. Wind speeds below 4.47 m sec-1 produced relatively greater increases in metabolism than wind speeds above 4.47 m sec-1. Changes in metabolism due to wind effects are discussed in terms of wind penetration of the feather coat and changes in boundary layer conditions. Ecological implications of cold weather conditions and their effect on kestrels are also discussed. Radiation produced linear decreases in metabolism at all wind speeds, and it extended the thermoneutral zone to lower air temperatures. Predictions of raptor resting metabolism based on multiple regression models and on heat transfer analysis were similar, but biophysical estimates paralleled actual values better than regression estimates.
Hayes, Steven R., "The Combined Effects of Air Temperature, Wind, and Radiation on the Resting Metabolism of Avian Raptors" (1978). All Graduate Theses and Dissertations. 8053.
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