Patricia Thong started the discussion when she posted an image from her hand phone of one of two mynas puffing its feathers and opening its bill. The birds were under the noonday sun on a hot day. She wanted to know what was happening.
Sun Chong Hong sent in his image of a Javan Myna (Acridotheres javanicus) gaping (above left), adding, “The following answer is quoted from LINK. “Since birds have no sweat glands, heat must be lost through the respiratory tract by panting, or in non-passerines by the rapid vibration of the upper throat and thin floor of the mouth (“gular flutter”).
“To minimize the energy cost of temperature regulation (‘thermoregulation’), birds use a variety of morphological and behavioral traits to adjust their rates of heat loss and heat gain. Unfeathered (uninsulated) body surfaces serve as important sites for heat exchange with the environment. When heat-stressed, therefore, some birds, such as Black Vultures, excrete onto their unfeathered legs to increase heat loss by evaporation.”
Lena Chow directed both to an earlier post on the subject LINK while Dato’ Dr Amar-Singh HSS sent an image of the Olive-backed Sunbird (Cinnyris jugularis) with bill agape cooling off during a hot day in Ipoh, Malaysia (above right).
Patricia Thong, Sun Chong Hong, Lena Chow & Dato’ Dr Amar-Singh HSS