“Birds do not sweat, and extreme heat stresses their body temperature. They must remove this excess body heat through their respiratory system. You can see this when they can be seen panting like a dog,” (source).
Furthermore, Osprey mothers use their wings to shade fledglings from the sun when things warm up, and take a dip in the water to cool down while fishing. Read this blog post from The Audubon Society to learn more about birds in… well… heat!