Measurement of Maximum Oxygen Consumption in Guinea Fowl Numida meleagris Indicates That Birds and Mammals Display a Similar Diversity of Aerobic Scopes during Running

Judgement of exercise performance in birds has been hampered by a paucity of data on maximal aerobic capacity. We measured the maximal rate of oxygen consumption (V̇o2, max) in running guinea fowl Numida meleagris, a bird that has been used in several previous studies of avian running. Mean V̇o2, max during level treadmill running was 97.5 ± 3.7 mL O2 kg−1 min−1 (mean ± SEM, N = 5). V̇o2, max was on average 6% higher when the birds ran uphill compared with the value during level running (paired t-test, P = 0.041, N = 5). The mean basal rate of oxygen consumption (V̇o2, bmr) of the same individuals was 7.9 ± 0.5 mL O2 kg−1 min−1. Mean factorial aerobic scope based on individually measured values of V̇o2, max and V̇o2, bmr was 13.2 ± 0.6 (mean ± SEM, N = 5). This value was considerably lower than the factorial aerobic scope previously measured during running in Rhea americana, a large flightless ratite. The difference in factorial scope between these two running birds likely reflects the effects of body size as well as size-independent differences in the ability to deliver and use oxygen. These data confirm a previous prediction that birds have a diversity of factorial aerobic scopes similar to that exhibited by mammals.