How does Huang Yan think of age

Huang Yan wants to look at age, you can observe its feathers, or look at its paws. Generally, the young bird's hair color is bright, and the toenails on the paws are relatively short.The old bird's feathers are more messy, and they are not so bright. The toenails are long, the skin on the legs will be white, and there are some keratin.In addition to buying this kind of bird, you have to buy a smaller one, but it depends on its spirit or not, is there any injury on your body?