If your cockatiel is showing signs of falling, not being able to perch, or overall weakness, you should seek avian veterinarian attention as soon as possible. A cockatiel that does not perch or loses its balance is a sign of a sick bird.
Infections, undesirable high toxic levels in your cockatiels body like lead, tumors, and lack of certain vitamins can make your bird lose its balance.
If your cockatiel has recently injured herself by crashing against a mirror or a window, it might be suffering from head trauma, vet attention is required.
Kitchen fumes can also make your cockatiel sick, and lose its balance, it takes very little for a cockatiel to die from kitchen fumes, specially if your cookware is made with teflon.
If your cockatiel is taking prescribed medication from your vet and started to lose its balance after the medication was prescribed, stop the medication and call your vet, it might be and undesired side effect.
You know that old saying like a "canary in a coal mine", well there is so much truth in that when it comes to birds.
Canaries were once regularly used in coal mining as an early warning system. Toxic gases such as carbon monoxide or asphyxiant gases such as methane in the mine would kill the bird before affecting the miners.
Just like canaries, cockatiels have a very proficient and delicate respiratory system and fumes that you can't smell or see can be deadly for a cockatiel.
A cockatiel losing its balance is one of the first signs that dangerous fumes might be present in the house. If for example you are planning to clean your house it would be best to move your cockatiel to a well ventilated room where it is as far away as possible from cleaning fumes.
Other fumes that can hurt your bird are in the likes of aerosol sprays, toxic fumes from nonstick cookware, new carpet smell, fresh paint, room fresheners, scented candles, hair spray, perfumes, smoke, carpet cleaners, nail polish and many more.
As always the information offered here is to provide guidance and is not intended to be a substitute for the good advice provided by your own avian vet. When in doubt always consult your own veterinarian.