Photoperiod-induced changes in temperature-metabolism curve, shivering threshold and body temperature in the pigeon.

A short photophase combined with cold-acclimation changed the shivering threshold of the pigeon from 21 to 14 degrees C. The change of critical temperature was also found in the temperature-metabolism curve. A long photophase both alone and combined with warm-acclimation induced a reduction of body temperature to a lower level (about 2 degrees C) at all ambient temperature, ranging from 5 to 40 degrees C.