Why do many ducks form only brief pair bonds?

In the context of anseriform birds, the duration of pair bonds is closely linked to the life expectancy of the species. Geese and swans, which are long-lived, typically form lifelong pair bonds that are maintained through consistent social displays.1

In contrast, many ducks are shorter-lived and generally form only brief pair bonds. While the specific evolutionary pressures for this behavior are complex, the male's role in the reproductive cycle is a significant factor: once the female begins to incubate her eggs, the male duck typically deserts her to join other males, often participating in a molt-migration. This departure contrasts with geese and swans, where the male remains to molt with the female and their family. Consequently, the pair bond in many duck species is functional for the purpose of mating and courtship but does not extend through the duration of chick-rearing.12