HEAT-PRODUCTION INDUCED BY PHOTOPERIODICITY IN THE PIGEON

1. 1. The effect of photoperiodicity on heat production was studied in pigeons (Columba livia) acclimated to 12L:12D, 24D, 4L:20D and 24L at Ta = 22°C, to 4L:20D at Ta = 32°C and to 24L at Ta = 2°C. 2. 2. Pigeons acclimated to 4L:20D at Ta = 22°C increased oxygen consumption significantly (P < 0.05) at Ta= 26°C and Ta = 6°C, compared to the control group (12L:12D at Ta = 22°C). Body weight in these birds decreased significantly (P < 0.01 ) due to acclimation. 3. 3. Oxygen consumption was high but not significantly increased in pigeons acclimated to cycles of 4L:20D at Ta = 32°C and 24L at a = 2°C. 4. 4. Pigeons acclimated to 24D were significantly hypothermie (P < 0.01) due to acclimation (at Ta = 22°C), while no change in body weight was observed. 5. 5. Photoperiod influences heat production to a similar degree as does ambient temperature. Acclimation to cycles of a long scotophase had the same effect on heat production as acclimation to a cold ambient temperature. © 1979.