Birds have poor heat tolerance. They do not have means to dissipate
body heat such as sweating. The feathers insulate the heat and retain
the heat instead of dissipating it. In a hot day, you can observe
birds with their beaks open.
Some birds simply can not tolerate the
heat. The photo shows a starling lying on turf spreading its wings.
The way the birds sleep
Water fowls sleep on one of their legs while keeping another leg up.
In that way, they keep the circulation of blood. The photo shows
Cygnus buccinator in sleep with one of its legs up.
