What is going on with the buttocks of the Bird Bird?

Ban Wenbird's buttocks may be a bad thing or sick. It may be sick. You need to replace food in normal times, clean them regularly, and use Urban Success to mix water for water.This kind of bird is the same as the genus of Wenbird. It prefers group activities and is widely distributed in Asia. It can be seen in the southern region of my country.It has a large number and is harmful to agriculture, so it is tamed to control the number as an ornamental bird.