It is known that birds' feathers would fall off and replaced with new ones. Species with a breeding plumage would change their feathers two times each year, while for others the change may be gradually. This is called moulting. For some Common Myna, it may occurs all at once at the head and neck, and the bird become bald. Though it's look may be strange from others, but it is still allowed to associate in the flock.
Myna community in SRF.