TEMPERATURE REGULATION IN WHITE-TAILED PTARMIGAN LAGOPUS LEUCURUS

1. 1. Standard metabolic rate of 48·8 kcal/24 hr for the white-tailed ptarmigan (Lagopus leucurus) is slightly higher than expected and may be associated with the continuous molt in this species. 2. 2. The lower critical temperature (6·5-11·5°C) is one of the lowest values recorded for birds and reflects the ptarmigan's excellent insulation. 3. 3. The ptarmigan has the lowest evaporative efficiency recorded in birds. Differences in efficiency of evaporative cooling may be adaptive, since they are correlated with habitat. 4. 4. Ambient temperature may be an important factor in habitat selection in some cases. © 1968.