Most ducks do not have only one mate. While they form a pair bond—a type of social monogamy where a male and female stay together—this pairing is almost always temporary. It lasts only for a single breeding season, a system known as seasonal or serial monogamy. This bond is distinct from genetic monogamy, as the pair stays together for protection, but genetic testing often reveals that not all offspring are sired by the bonded male.
The Nature of Duck Pair Bonds
The standard mating system for most species in the duck family (Anatidae) is based on a seasonal bond rather than a lifelong commitment. Pairs often form early, sometimes in December or January, on the wintering grounds or during migration. This early pairing allows the female time to select a high-quality mate and be ready to nest upon reaching the breeding grounds.
The pair bond is maintained for several months, typically lasting four to eight months, and its primary function is protective. The male, or drake, defends the female from the harassment of unpaired males leading up to egg fertilization. This defense ensures the female can feed and build the necessary energy reserves to produce a clutch of eggs. The bond dissolves once the female begins incubation or shortly after she finishes laying her eggs.
Diversity in Mating Strategies
The social pairing of ducks rarely translates into genetic fidelity. Extra-pair copulations (EPCs) are common, meaning the bonded female mates with males other than her partner. Studies on species like the Mallard estimate that a significant percentage of clutches contain offspring sired by multiple fathers.
This genetic complexity is intensified by the prevalence of forced copulation, documented in over 50 species of Anatidae. These aggressive acts, often initiated by unpaired males, are known as forced extra-pair copulations (FEPCs). While most ducks follow the seasonal pairing model, some sea ducks, such as Eiders or certain Goldeneye, demonstrate stronger philopatry. This means they return to the same sites, which can lead to pairs reuniting for several consecutive seasons.
Courtship Rituals and Displays
Before a pair bond is established, males engage in elaborate, highly ritualized courtship displays. These displays serve as a behavioral audition, often taking place in groups with multiple drakes vying for a single female’s attention. The female assesses the males’ vigor, plumage, and display quality before making her choice.
A drake’s performance includes specific, rapid motions like the “Head-Up-Tail-Up” display, where the male raises his tail and wings while whistling. Other movements include head-pumping and the “Grunt-Whistle,” a complex vocal and physical gesture. If a female accepts a male’s advances, she signals interest by performing “Nod-Swimming,” a rapid, low-swimming motion that encourages the male to follow her away from the group.
Parental Roles and Investment
Once copulation occurs and the female is ready to nest, the pair bond terminates abruptly, highlighting the minimal parental investment by the male. The female selects the nest site, builds the nest, and handles the entire incubation process alone. She also takes sole responsibility for rearing the precocial ducklings, which can feed themselves almost immediately after hatching.
The drake typically abandons the female as she lays her final eggs or begins incubation. He then gathers with other males in bachelor groups, often migrating to a safe location to undergo a complete, vulnerable molt of his flight feathers. This division of labor confirms that the duck pair bond is purely a reproductive strategy aimed at ensuring fertilization and protecting the female, not a partnership for raising young.