Why do cockatiels ruffle there feathers?

I'm not sure If this is what you are asking but they pluck their feathers out because it's like brushing your hair, you purposely don't pull your hair out neither do birds. It can look excessive because it could be when the bird is molting (shedding feathers to make way for new growth) but if the bird starts to develop patches of missing feathers you will need to take it to a vet. That's not how molting works.