By Mike Brasher, Ph.D.
Experienced waterfowl hunters know that ducks respond differently to calling throughout fall and winter. Although habitat conditions
, and local hunting pressure can also play a role in the birds' willingness to decoy, courtship and pairing activities are responsible for many of the changes in waterfowl behavior
observed during hunting season. Understanding these behaviors is not only enlightening from a biological standpoint, but also necessary for developing responsible harvest regulations and may even help hunters bag more birds.
A quick refresher on waterfowl mating systems
is needed to appreciate the significance of courtship and pair formation to waterfowl. All waterfowl are essentially monogamous, meaning one female will pair with only one male. Geese, swans, and whistling ducks are classic examples of species
that form lifelong pair bonds (perennial monogamy), while most species of ducks form pair bonds that last only four to eight months, often with a new mate each year (seasonal monogamy). As a result, most ducks undergo courtship and pair formation annually, while geese, swans, and whistling ducks do so only when acquiring a mate for the first time, when a mate dies, or in rare instances when paired birds become geographically separated.
PAIRS, HARVEST AND MATE LOSS When a paired bird is harvested by a hunter, its mate must find a suitable replacement. Most waterfowl establish new pair bonds within days or weeks after losing a mate, but the timing of the loss can have an impact on the birds' survival and productivity. In recent studies, female black brant that lost mates during the hunting season subsequently found new ones, but experienced higher mortality than birds that did not lose mates, likely because of a greater vulnerability to harvest and predation during the courtship and pairing process. In another study, researchers used controlled experiments to demonstrate that among female mallards, the loss of a mate in late winter may reduce annual recruitment by as much as 7 percent. The increased time and energy costs associated with finding a new mate were believed to have been responsible for the decreased productivity in these birds. This information is vital to ensure that hunting season dates and lengths are rooted in science and compatible with the reproductive behaviors of waterfowl populations. Rigorous consideration and application of the latest scientific findings will help waterfowl managers maintain healthy populations of ducks and geese for future generations to enjoy.
A defining characteristic of seasonal monogamy is the weakening of pair bonds during summer as female ducks nest and begin incubation. Previously paired males leave the breeding grounds for traditional molting sites while females incubate their eggs and raise their broods. During fall, large concentrations of ducks gather on staging areas and eventually begin their southward migration. It is during this time that the annual pair-formation process begins. Although the exact timing varies among species, courtship activity in ducks starts gradually on northern staging areas and ultimately reaches a fever pitch during winter and early spring at middle and southern latitudes. If you have ever wondered why ducks don't respond as well to calling early in the fall as they do later in the season, now you know the reason.
The pattern of early pairing for ducks is unique in the bird world, as most species of seasonally monogamous birds, such as migratory songbirds, delay courtship and pairing until spring or summer. This has been a topic of much study and debate among biologists. Attempts to explain this behavior have relied heavily on comparisons among species and taxonomic groups.