Exhaled air temperature as a function of ambient temperature in flying and resting ducks

Exhaled air temperature (T exh) has a paramount effect on respiratory water loss during flight. For migratory birds, low T exh potentially reduces water loss and increases flight range. However, only three studies provide empirical data on T exh during flight. The aim of this study was to record T exh of birds during rest and flight at a range of controlled ambient temperatures (T amb). One wigeon and two teal flew a total of 20 times in a wind tunnel at T amb ranging from 1° to 24°C. T exh during flight did not differ between the two species and was strongly correlated with T amb (T exh=1.036 T amb + 13.426; R²=0.58). In addition, body temperature had a weak positive effect on T exh. At a given T amb, T exh was about 5°C higher during flight than at rest.