Hi,
I’m not sure if you mean you found this bird outside somewhere or if this is your pet. Either way, a head or spinal injury would not necessarily be apparent, and could certainly cause this type paralysis. If this is the case, it may take weeks or months or even a year, but the bird may slowly recover. However, if this bird was found wild, outside, it could have a disease such as a viral infection. Or it may have been poisoned. Depending on where you live, there is still an ongoing Avian Flu outbreak, and the bird could have this. If the bird has a disease or was poisoned, there is nothing you can do and it will die soon. If it continues to survive, then you need to provide a safe enclosure with padding on the floor so the bird doesn’t get injured while moving around. Then it is mainly a matter of waiting and seeing if he improves over time. You can ask the Vet about giving the bird an anti-inflammatory drug.
Take care,
Brenda