干旱区生态环境知识资源中心

The metabolic physiology of the Crested Pigeon (Ocyphaps lophotes) and the Brush Bronzewing (Phaps elegans) is generally similar to that expected for birds of their size, but the Crested Pigeon has a number of characteristics which would aid survival in hot and dry regions. Body temperature increased similarly for the Crested Pigeon (from 38.8 degreesC to 41.5 degreesC) and the Brush Bronzewing (39.3 degreesC to 41.4 degreesC) over ambient temperatures (TaS) from 10 degreesC to 35 degreesC. Both species became hyperthermic (body temperature, T-b > 42 degreesC) at T-a = 45 degreesC. Basal metabolic rate of the Crested Pigeon (0.65 ml O-2 g(-1) h(-1) at 40 degreesC) was similar to71% of that predicted for a columbid bird, while BMR of the Brush Bronzewing (0.87 ml O-2 g(-1) h(-1) at 20 degreesC to 40 degreesC) was similar to102% of predicted. Total evaporative water loss increased exponentially with Ta for both species, from <1 mg H2O g(-1) h(-1) at 10 degreesC to > 12 mg H2O g(-1) h(-1) at 45 degreesC. It was similar and low for both species at Ta < 30 degreesC, but was higher for the Brush Bronzewing than the Crested Pigeon at T-a > 30 degreesC. Ventilatory minute volume matched oxygen consumption, such that oxygen extraction efficiency did not change with T-a and was similar for both species (-20%). Expired air temperature was considerably lower than T-b for both species at Ta < 35 degreesC, potentially reducing respiratory water loss by similar to65% at T-a = 10 degreesC to similar to30% at T-a = 35 degreesC. Cutaneous evaporative cooling was significant for both species, with skin resistance decreasing as T,, increased. The Crested Pigeon had a lower skin resistance than the Brush Bronzewing at T-a = 45 degreesC. The Brush Bronzewing had apparently reached its maximum cutaneous water loss at 30 degreesC and relied on panting to cool at higher T-a.