Mallard Hens Shaking Fanny Tails

We have a community pond in our townhouse development, stocked with fish, and visited by many birds, including eagles, various egrets and herons, and a daily osprey. We also have some mallards who make the pond their home. Recently, two different couples had some ducklings. I feed them cracked corn. It’s a real show seeing the parents watch over their children, keeping an eagle eye out for stray cats (and some not so stray), and ensuring that their kids get to eat first. When non-family mallards come to enjoy the feast, the drake will shoo them out by lowering his neck, beak extended, and threatening to stab the intruder. I’ve seen a hen do the same to a drake. Even a duckling has done it to a much larger drake. (Sometimes the intruder will do it to the mother hen or father drake and the family runs away.) My question?Sometimes after a hen has been shooed away in this fashion, she will stop and wag her tail (undertail coverts?). This seems to indicate “uncle,” and the chase ceases. Is my interpretation correct? And BTW a big drake should not be afraid of a small duckling, yet the drake runs away. Some kind of ingrained behavior?