Can cockatiels re-grow feathers?

Cockatiels will only re-grow feathers in the presence of other cockatiels. For optimum regrowth, the number is very specific: 17 must be present, and the birds must be loosely positioned in a circular shape (either in captivity or in the wild). Although re-growth is possible with other numbers, it is not desirable as it can lead to infections of the gland and claw.