INFLUENCE OF WIND-SPEED ON SAGE GROUSE METABOLISM

We measured the effect of wind speed on the metabolic rate of six adult sage grouse (Centrocercus urophasianus) with indirect respiration calorimetry at ambient temperatures above, near, and below the lower critical temperature. There was a significant effect (P < 0.05) of temperature on metabolic rate at all wind speeds, and a significant effect (P < 0.05) of wind speed on metabolic rate for temperatures less than or equal to 0 degrees C. Wind speed had a more pronounced effect on metabolism at temperatures below the lower critical temperature for sage grouse. Metabolic rates measured at wind speeds of greater than or equal to 1.5 m/s were significantly higher than those measured at wind speeds < 1.5 m/s. Multiple regression analysis of wind speed (u; m/s) and temperature (T-a; degrees C) on metabolism (MR; mL O-2 . g(-1). h(-1)) yielded the equation MR = 0.0837 (u) - 0.0248 (T-a) + 0.5444. The predicted cost of thermoregulation at conditions of -5 degrees C and u = 1.5 mis was about 1.5 x standard metabolic rate; half the increase was due to wind. Measurements of wind speed in sagebrush (Artemisia spp.) stands indicate that such habitat effectively reduces wind speed to < 1.5 m/s. Microhabitat value should be recognized in the management of sagebrush stands.