It was a scorcher in Satara Camp. Initially I thought this grey go-away-bird tried to deal with the 45deg C midday heat by hugging the cooler soil.
While birds do not have sweat glands, physical characteristics that help birds in hot climates keep cool include:
1. Respiration Rate: Birds have rapid respiration rates that allow greater heat dissipation than regular breathing would.
2. Bare Skin: Bare skin patches on the legs, feet and face allow greater heat loss than if all areas were covered with feathers. Even small patches such as a fleshy eye ring can help dissipate heat.
3. Bill Size: Birds with large bills have a rich blood supply to their beaks. On a hot day, the birds can increase the blood flow to their bills to help release heat, but when the temperature cools that blood flow slows and heat is retained.
Mind you, I have been thinking about (and reading up on) the observed go-away-bird action of spread-eagling out in the full heat of the midday sunlight. Its gaping and panting makes me think that these birds were not comfortable at all and that it is unlikely to be an adaptation to cool themselves, but rather them performing an obviously uncomfortable action to reduce louse infestations by sunning. Scientists have found that air temperatures slightly above 40 degrees Celsius can be lethal to lice and their eggs. Birds were observed to groom extensively following sunbathing, likely in order to remove the dead lice. After sunning they have to spend less time rooting out each live one individually by preening only.