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

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