Night frights can be caused by a noise inside the house or the outside that wakes your bird suddenly. Headlights from a car driving by could also cause this. If your bird's cage is located near a window, he or she might have seen an animal or the shadow of an animal moving past outside.
Usually, you have no idea what caused it, but everything seems quiet & peaceful when suddenly your bird begins flying in the dark and banging into the sides of the cage before finally landing on the cage floor.
Some birds are more prone to night frights than other birds and if you have more than one bird, it is possible that one bird has night frights which causes other birds in the same area to also leave their perches.
Injuries that can happen during a night fright include broken wing or tail feathers including blood feathers that obviously mean the loss of some blood. Since the bird can not see where he or she is flying, wings can bang on a perches, cage bars or toys hard enough to bruise. On rare occasions, a wing or leg could be broken or even death can happen if the bird hits something at an angle that breaks a neck or causes the bird to fall a distance to the ground.
Many birds never have night frights and in that case this is something you may never have to worry about. Some birds have them, but very rarely and these can be solved by turning on a light and talking to your bird to calm him or her down. It will take your bird at least a few minutes to settle down and get comfortable again, so do not turn off the light too soon, or leave it on for the rest of the night.
Some birds benefit by sleeping in a small night cage, which is generally covered at night. A noise might still startle them, but the small size of the cage reduces the risk of injury if it does happen.
A night light in the room with your birds will make it easier for them to get back to their perches if they are kept in larger cages or flights.