Body temperatures of black-capped chickadees P. atricapillus acclimatized to winter in Fairbanks, Alaska (USA, 65.degree. N lat [latitude]), measured during the night at ambient temperatures from 27 to 50.degree. C, averaged 38.5.degree. C, a decrease of 3.degree. C below daytime body temperature. Metabolic rates at night increased with decreasing ambient temperatures. No evidence of the degree of nocturnal hypothermia observed in Scandinavian or more temperatre latitude parids was observed in these Alaskan birds.