senegal suddenly losing belly feathers

Our 10 year old senegal parrot in last 3-4 days is suddenly just flapping wings & losing the belly feathers. Looks bald now on belly. They are the small white/green/gray soft feathers. Does not seem to be plucking. Just flaps & all the feathers fly off. Have not seen anything like this before. Nothing has changed. Eats pellets & fresh produce. We do have a woodstove & house a little dry but this is situation every winter. She is eating fine & no change in excrement. Can you help us?