The body of a duck is designed in a way to resist cold. You will find that under normal circumstances, most ducks will resist cold to some degree.
Pekins are a large breed with an average weight of 8 to 11 pounds. Going by this size, you can guess that they would tolerate cold to a decent degree.
This musculature might just be one of the reasons members of the breed as cold-hardy. In fact, no other breed matches this breed in meat yield.
The hardiness of Mallard ducks is also seen in their embryos. Mallards migrate in winter because the change in weather affects their access to food.
Overall, ducks are resistant to cold. Ducks have extra layers of fat, thick plumage, and their oily preen gland – all features that insulate them in cold weather.