“It was hot at Sg. Balang in the Johor state of Malaysia. The birds were taking cover under shade, but some like the Blue-tailed Bee-Eater (Merops philippinus), were out in the open under the hot sun, perched on bamboo poles, and other places of vantage points, looking out for insects. However it could be seen that their bills were wide open and sometimes their tongues could also be seen lifted just above the lower mandible.
“So the question now is do birds perspire? Well, they don’t, as they do not have sweat glands, unlike mammals. Heat loss in birds is undertaken through evaporation of water from the surface of the body. This cools the blood flowing just beneath the skin.
“When a bird opens its mouth and pants, it increases the area of the body that is exposed to the air. The evaporation of water vapour from the lungs and air sacs further helps to remove excess heat.
“Thus in very hot conditions birds can be seen breathing very fast with their mouths open to expel any excess heat that their bodies cannot cope with. And in hot weather, birds look much thinner than their cousins in colder climates as the latter tend to fluff their feathers to cut down heat loss.”
3rd October 2009