Re: Winter cluster generating heat
When a human, or other mammal, gets cold and starts shivering, the shivering action is a series of small contractions of muscles, and generates heat. Even though your arm muscles may be moving in a shivering action, your arms themselves are not moving significantly.
I haven't found a reference that says whether bees have a way of disconnecting both sets of wings or just one set, but either way I suspect that bees can engage in a shivering type action that exercises their wing muscles ( and generates heat) without making their wings move back and forth appreciably.
--- Victor Hugo - "Common sense is in spite of, not the result of, education.