Like me, they were simply hot. Unlike people however, birds lack sweat glands and so cannot sweat to cool themselves down. But birds call on a variety of innovative techniques to beat the heat. Vultures and other large soaring birds also cool themselves by riding thermals to several thousand feet up in the atmosphere where the air may be 50 degrees cooler than on the ground. And they increase circulation to unfeathered parts that will radiate heat from their blood to the outside air.
Most birds can dissipate about half of their resting heat production by panting.
Sweat began to trickle down my back as I stood watching the two birds. After a moment, I walked on, headed for the air-conditioned campus library. As I pulled open the door, releasing a gush of cool air, I looked back. The thrasher and the white-winged dove sat motionless in the shade, their mouths open, panting.