In regard to mechanical bird repairs: The "drums", as you call them,
are actually rubber covers or in some respect, bellows. They have been
available from a clock parts company, R.S. LaRose. I don't have their
address or phone but you might find them on the Web or through a clock
repair person for sure.
[ The firm's Internet domain name is registered to this address:
[ S. Larose, Inc.
[ 3223 Yanceyville Street
[ Greensboro, NC 27405 USA
[ tel.: 203-798-0810
[ -- Robbie