The role of plumage and heat dissipation areas in thermoregulation in doves.

Avian plumage contributes to the regulation of body temperature. In most climates, avian heat dissipation occurs passively via radiation, conduction and convection owing to the thermal gradient between the environment and the animal. The muscles that power flight also produce significant heat that must be dissipated. How plumage and areas with sparse or no feathers (termed 'heat dissipation areas', HDAs) interact with these mechanisms is unclear. We examined the role of plumage as an insulator, or dissipator, of heat in ringed turtle-doves (Streptopelia risoria) under four thermal regimes: resting, post-flight, heating via radiative lamps, and cooling via wind. We measured internal body temperature and skin-level temperature (under the plumage) using thermal PIT tags alongside surface temperature using a thermal imaging camera. Flight increased internal temperature by 0.6°C compared with resting, but the other treatments did not have significant effects. The skin-level temperature during wind exposure was 1.6°C cooler than in other conditions. HDAs changed in surface area above 35°C but not maximum temperature among treatments. Post-flight and during radiant heating, birds increased HDA surface area - most notably at the wing. During simulated wind produced using a fan, the HDAs of the beak and wing were eliminated, and areas of other HDAs were reduced. Our results demonstrate that birds modulate active HDAs to maintain consistent core body temperatures under induced temperature challenges. They also promote caution for extrapolating from thermal images of surface temperature to infer core temperature in birds.