Female mallard ducks can only relax when in constant contact with their families. Why? These fowl are the number one menu choice for foxes and many other predators. But as long as they keep quacking, they can call their young and keep their families together. But doesn’t that get exhausting? Well, mallards quack so much that their calls are in sync with their breathing, and happen automatically. When they flap their wings down during flight, their muscles contract into the chest cavity; then when they exhale, they quack. The faster they fly, the louder their calls to their families.