I don't! - But the Mallard drakes always under-estimate my ducks every spring and receive some hard lessons:Frank don't under estimate the wild Mallard drakes. My neighbor works at a company that has a large pond. He eats lunch outside when it is nice and watches the Hens get drowned. The Mallard Drakes will pile three on one in the water and she doesn't have a chance. If yours have always been around the wild ones and been fine that is good. Here they don't have a chance if there are drakes around.
The Indian Runners simply out-swim and out-dive the Mallards.
And the larger breeds, you can pile five Mallard drakes on top of Blanca and she would still be over water. - Before she would start to eat those drakes.
And my drakes fiercely defend their girls, with Boots looking like an aircraft-carrier vs. a dinghy compared to a Mallard.
I'm more concerned about my drakes drowning my ducks.