Conflict also arises when an intruding mallard pair attempts to settle on a pond that is already occupied by another pair. In these instances, the resident male quickly pursues the intruding female to drive her away. This often leads to a twisting and towering “three-bird flight,” where the intruding female flees from the determined resident drake. The intruding hen’s mate trails helplessly behind during the chase without making much of an attempt to defend her. These flights may last for several minutes and extend up to a half mile or more away from the pond where the chase began. Once the intruding hen has been driven far enough away, the resident male turns back, setting his wings and making a long glide back to the pond and his waiting mate. He can’t be away too long or other males may take advantage of his absence. These “three-bird flights” are a common sight on the breeding grounds during spring.
A paired male mallard will remain intolerant of other males and pairs until his mate has finished laying her eggs and begins incubation. Only then will he abandon the hen and pond that he had previously defended so vigorously. At this point, he may attempt to breed with other paired females in the area that are still in the process of laying eggs, or he may pair with another hen whose first nesting attempt has failed. In the latter case, the drake will once again actively defend the hen and the pond chosen by his new mate.
The male’s strong defense of his mate helps ensure that he will “sire” a higher number of ducklings in the next generation. This can be thought of as a type of paternity defense. For the female, the likely advantage is she breeds with a male that is capable of defending her and the breeding pond and is therefore a good choice to fertilize her eggs. Her mate also helps ensure that she will be relatively undisturbed while feeding during the energy-demanding laying period.
There are other apparent reasons why waterfowl disperse widely in breeding habitats. For one, hatched ducklings are not able to fly and initially depend largely on food resources in the area previously defended by their mother’s mate. By keeping other pairs away from the pond, resident males help ensure that, in the future, the ducklings will not have to compete with other broods of the same species for limited food supplies.
Indeed, biologists believe that one of the main reasons that fewer birds attempt to breed during dry years is there simply isn’t enough habitat to support breeding hens and, later, their broods. Females with mates that are capable of defending their chosen breeding ponds occupy all the suitable habitat, forcing other pairs to move to other regions or to forgo breeding altogether.
Another reason breeding waterfowl disperse widely across the landscape is to limit their vulnerability to predators. Large numbers of breeding birds and nests concentrated in a small area are more visible and produce more scent, both of which could attract predators. Conversely, isolation of pairs and nests in the best breeding cover possible can significantly reduce their odds of being discovered by predators.
Regardless of why breeding waterfowl seek isolation, spring is a fascinating time of year to visit wetlands and watch the birds demonstrate a variety of behaviors in defense of their mates and habitat. If mallards breed on a pond near your home, you will probably be able to watch the drama unfold right in front of you. And if other waterfowl species are present, you can observe interesting variations on the same basic theme.
Dr. Bruce Batt recently retired after a long tenure as chief biologist at DU’s national headquarters in Memphis.