Body and Egg Temperature Regulation in Incubating Pigeons Exposed to Heat Stress: The Role of Skin Evaporation

The rock pigeon (Columba livia) reproduces successfully in breeding colonies at ambient temperatures (Ta) exceeding 50 C. Unusually low body temperatures (Tb) of 38.9 C (±0.6 SD) and 40.0 C (±0.5 SD) were measured during incubation at 45 and 50 C Ta. Egg temperature (Tegg) was regulated at 36.7 C (±0.8 SD), 39.0 C (±0.6 SD), and 40.7 C (±0.6 SD) at 28, 45, and 50 C Ta, respectively. The incubating birds (acclimated to high Ta's) use an effective cutaneous evaporative cooling mechanism in lieu of panting or gular flutter. Incubating birds achieved heat and water balance while exposed to extreme thermal stress by using an efficient cutaneous evaporation cooling mechanism, avoiding nonessential activity, and maintaining low metabolic rates.