Do not place your bird's cage in an area that receives direct sunlight (especially by a window that reflects the heat of the afternoon sun), and do not leave your pet bird in a parked car in the sun (never leave your bird in a parked car--period). The overheated bird will pant (birds do not sweat), hold its wings away from its body and appear "slick" (hold its feathers tight to its body). It may also drink large amounts of water if available. Heatstroke may occur, resulting in permanent brain damage.
Signs of heatstroke also include: weaknesses, a dazed expression, dry skin and, ultimately, collapse. If your bird is exhibiting any or all of the above signs, try to reduce its body temperature immediately by spraying it with cool water, offering it water to drink or by placing its feet in a cool bath. Shock may occur, so keep the bird calm, and take it to the veterinarian immediately.