What's wrong with the crow's tail hair?

The crow's tail hair fell off, indicating that it would change the hair.This bird will change twice a year, once in spring, and the other in autumn.When changing hair, be sure to put it in a place without wind, and keep it quiet.Usually you can feed some nutritious feeds to promote the growth of new feathers.In addition, it is necessary to clean it to ensure that it is clean in the cage without much dirty things to prevent it from getting sick.