My conure jerks his head up and down repeatedly. Is this normal behavior or is he having a seizure?
If he’s doing this when he’s interacting with you or a toy or a mirror, it could simply be that he’s regurgitating as a sign of affection. Most parrots do this and they start it quite young. It can be quite an active and violent-looking activity. But if he’s not doing much of anything and he suddenly starts shaking it could be a symptom of illness. In that case, it would be advisable to call your avian vet and ask about any new behavior.