By Bruce Batt, Ph.D.
Gregarious throughout much of the year, waterfowl seek isolation during the breeding season
All waterfowlers enjoy seeing large numbers of waterfowl, especially from a blind during the hunting season. Indeed, one aspect of waterfowl behavior that people find most compelling is the birds’ propensity to gather in spectacular concentrations on staging, migration, and wintering areas.
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While ducks and geese are drawn together socially throughout most of the year, the opposite is true during the breeding season. At this time, breeding pairs seek isolation and can be downright unsociable. Visit the famous Prairie Pothole Region at the height of breeding season, and you will see pairs of various waterfowl species scattered here and there on wetlands, but few large flocks. In fact, after hens begin incubating their eggs, it can be surprisingly quiet on the breeding grounds.
Breeding waterfowl isolate themselves from rival pairs in many ways. As an example, let’s look at the mallard, which can be observed just about anywhere there is suitable habitat. After selecting a mate on the wintering grounds, a female mallard will typically lead her chosen drake back to the area where she was raised—often to the same pond. The male stays close to her side and is diligent about defending her from the advances of other males. Males greatly outnumber females in many duck populations, so competition is often fierce among drakes for prospective mates.
Soon after a mallard pair arrives on the breeding grounds, the birds take up residence on a small wetland or a portion of a larger one. After the hen has made a nest—usually in adjacent upland cover—she begins laying eggs, usually at the rate of one egg a day. While the hen is away, the drake stays behind to defend their wetland. This is where the female spends most of her time feeding and where the pair copulates frequently to help assure that each egg is fertilized.
When unmated drake mallards intrude on a pair’s space in search of potential mates or breeding opportunities with a paired hen, the resident drake will stay close by the hen’s side and try to prevent the intruders from copulating with his mate. He is not always successful, as mallard broods often include ducklings “fathered” by different males.