Gas exchange and energy cost of flight in the white-necked raven, Corvus cryptoleucus.

Energy expenditure during steady-state, wind tunnel flights was estimated from O2 and CO2 exchange in five white-necked ravens (Corvus cryptoleucus, mean mass, 0.48 kg) at air speeds of 8-11 m/s. Power input was closely similar to allometric predictions based on data from other species of smaller birds. It increased significantly with air speed and flight angle above horizontal, and decreased with increasing angles below horizontal. Maximum power input reached seven times the preflight value measured under resting but not basal conditions, 14 times the previously measured basal values and three times the calculated maximum for a similar sized running mammal. Energy cost to travel 1 km decreased with increasing air speed. These trends are similar to those previously observed in smaller birds.