The Coo coo clock was given to us by my Mother's father, Grandpa Andy (Emanuel Anderson), in the mid 1950's. And yes, the weights really make the clock and coo coo operate! For your viewing pleasure I will post two videos, one showing the coo coo bird, the second showing the weight and chain move.
Here is the 10 o'clock coo coo.
Here is the chain moving.
All this with no batteries! The clock operates about 5 days on chain length. Phineas Fogg would be proud.