Reproduction of rock pigeon exposed to extreme ambient temperatures

1. 1. The breeding biology of rock pigeon (Columba livia) exposed to ambient temperatures (T_a) between 50 and 60°C was investigated. 2. 2. Four families accomplished three complete life cycles after long term daily exposure to extreme T_a, with about 100% success. 3. 3. The steady state temperatures in the nest were 60, 58, 53 and 44.6°C in the air, substrate surface, underwing, and in the egg's microenvironment, respectively. 4. 4. At thermal conditions between 30 and 60°C, egg temperature (T_egg) was regulated between 36.8 ± 0.8 (S.D.) and 41.7 + 0.4 (S.D.). T_egg increases by 0.163°C/1°C rise in T_a. 5. 5. Mean T_b of the nonincubating parent exposed to 30-60°C is 41.6 ± 0.6°C (S.D.). Under the same conditions the incubating parent regulated a significantly (P < 0.01) lower T_b (38.8°C) at 45°C T_a and about 1°C lower T_b at 30 and 60°C T_a, respectively. 6. 6. By comparing the differences between fast (5 min) cooling of hot egg (44.8°C) to slow heating (60-90 min), we could demonstrate the high sensitivity of the incubating parent to the danger of embryo overheating. 7. 7. The significance of the adaptive behavioral and physiological mechanisms in breeding under extreme thermal conditions are discussed.