Birds such as cockatiels need the ultraviolet light in sunlight in order to properly absorb vitamin D. Getting sunlight through a glass window filters out the crucial ultraviolet light.
If the weather is warm enough, the window can be opened, as long as it is screened so that the cockatiel cannot escape. Roll the cage partially in the light cast from the window.
Place water and a shaded area in the cage so the bird can get shade if necessary. If the cage cannot be moved, place the cockatiel, the water and the shaded area in a smaller cage that can be transported about.
The Cockatiel Foundation recommends letting cockatiels indulge in supervised sunbaths in order to avoid vitamin D deficiency. Vitamin D deficiency causes weak bones and beaks because vitamin D helps the bird's body absorb calcium.
Cockatiels only need about ten minutes of exposure to direct sunlight. Even in this short time, part of the main cage or portable traveling cage needs to be partially covered for shade in case of heat exposure.
Cockatiels suffering from heat exposure will pant with open beaks and stretch their wings from their bodies in an attempt to cool off. If left untreated, the cockatiel will go into shock or seizures and die.
Transport the bird immediately to a cool area. Mist the afflicted bird with cool water.
Wet a towel or washcloth with cool water and wrap around the bird. If the bird is still conscious and active, offer cool water in a shallow dish so the bird can bathe or even just sit in the water.
Contact a vet as soon as possible.
Place portable cockatiel cages in warm rooms that do not get drafts and where the family or owner spends a lot of time. Bedrooms and living rooms work well, according to "Cockatiel: Your Happy, Healthy Pet" Keep the cage off the floor because cockatiels feel threatened by anything looming over them.
Keep cages away from ceiling fans or chandeliers. Ideally, cages need a wall behind them to help prevent drafts on one side and to help cockatiels feel more secure.
Never place cockatiel cages in bathrooms or kitchens because the smells can make the bird sick.