Primarily, birds off-load excess heat either by evaporative cooling directly through the skin or by panting. The latter method cools the bird's airways and helps lower an elevated internal temperature. A robin running across a lawn on a sunny afternoon with its beak agape is doing exactly that. To supplement panting, several species vibrate the muscles and bones in their throats, a tactic called gular fluttering. Bathing also beats the heat, as does ruffling feathers, seeking shade, and taking a siesta.
Cormorants chill by perching with wings outspread.
Other species, like black kites, ascend on thermals to reach higher, colder altitudes. Laysan albatrosses simply lean back to expose their feet to the breeze. Perhaps the most unique heat-dissipating antic belongs to some storks and New World vultures, which deliberately defecate on their legs. And conjugate on. For the next half-hour, the air is abuzz with their beating wings.