I have a couple questions... so birdie experts, give me some advice!

Do you cockatiels need gravel paper? The pet store said that Nelly would need it to digest her food, so we got her some, do they need it?

Do cockatiels molt during a certain time of the year? I have been noticed extra feathers in the bottom of Nelly's cage, could she possibly be molting?

How about those sandpaper perch covers? Do those help for anything?

Thanks!