Birds, much like other animals, use various means of thermorregulation. They don’t have sweat glands like humans do: instead, most of them open their beak. This is a common sight during hotter months: still birds with an open beak for no apparent reason.
Nontheless, cormorants use a much more curious method. They not only open their beak, but they also do a funny thing with their throat to pump air in order not to overheat.
A great cormorant exhibiting its Curious Cooling Conduct.
A young european stonechat with its beak open to dissipate heat.