Thermoregulatory behavior and body temperature in chicks of willow grouse (Lagopus lagopus lagopus)

Clocal temperatures (Tcl) of outdoor living captive willow grouse chicks (Lagopus lagopus lagopus) were found to increase from 39.4 +/- 0.5 degrees C. the first day to 40.3 +/- 0.5 degrees C. the twelfth day after hatching. Average Tcl of adults was 40.7 +/- 0.3 degrees C. When left alone for 30 min. in a controlled test environment providing temperatures ranging from 21 degrees C. to 46 degrees C., the one day old chicks preferred significantly higher ambient temperatures than eight day old birds. Tcl was significantly lower in the chicks tested the day after hatching than in the older chicks. It is concluded that the chicks' thermoregulatory behavior is essential for maintaining homeothermia, and that the birds' thermoregulatory set-point is low the day after hatching and climbs to adult level during the first week.