My cockatiel hurt its head and bled, now lethargy and not eating—what is wrong and how to treat it?

A cockatiel with lethargy and no eating after a head injury may have wound infection or pain; if the cause is unclear, internal injury cannot be ruled out, so see an exotic-animal vet promptly. If you cannot go, disinfect and medicate the wound: after bleeding stops, use iodine, then an anti-inflammatory ointment to prevent secondary infection; severe cases may need oral antibiotics once daily. With no appetite, offer millet, fruit and vegetables and syringe-feed nutrient fluid or glucose water to prevent dehydration.