By J. Michael Checkett
North American waterfowl nest across an immense geographical area ranging from the High Arctic to the marshes along the Gulf Coast. Reproductive strategies have evolved in keeping with the selective pressures (habitat variability, predation, etc.) associated with these varied environments. Renesting is one of several reproductive strategies employed by hens to exploit local conditions and improve the odds of successfully hatching a nest.
Nesting waterfowl live in an ever-changing environment where favorable wetland conditions may occur only four years out of 10. Predators loom, and tilling, haying and burning of peripheral cover during the nesting season further reduce available nesting habitat and destroy nests. Each year a large portion of the breeding duck population loses initial nest attempts, and individual hens must decide if they will attempt to nest again. Most will shift to new sites, and some may travel to new regions to continue the nesting effort.
Renesting, laying a replacement clutch following the loss of a previous nest, is an important reproductive strategy ducks of many species employ. It allows individual hens to have additional opportunities to hatch a nest after their earlier nesting attempts failed, compensating for high rates of initial nest loss common to ground-nesting birds. The old adage “persistence pays” has never held truer than for many waterfowl species. When nesting conditions are favorable, many duck species will go to great lengths to pull off a successful clutch. Whether a duck renests depends on many factors that vary annually and geographically, resulting in wide differences in renesting propensity and productivity among populations and species.
Renesting propensity generally varies with length of breeding season and depends on stage of incubation and date at the time of nest loss. Further, older birds may be more likely to renest, possibly because they tend to begin nesting earlier and may be in better physical condition. Productive wetlands are also vital for nesting because they provide hens with the nutrients required for egg production. Favorable habitat conditions benefit ducks in many ways, but good wetland conditions, allowing for adequate body reserves for egg laying and providing food and cover for ducklings, are believed to be the major factor affecting frequency of renesting. Conversely, in years of average conditions or areas with poor habitat, birds will be less likely to try to renest, and in drought years, some may forego nesting altogether.
Renesting behavior is different for each duck and goose species. Mallards, for example, are more likely to renest than are lesser scaup and gadwalls, because mallards are early nesters (three to four weeks earlier). If a mallard hen’s first nest fails, she usually has time left to renest and have the brood gain flight before the end of the brood-rearing season. Mallards have been documented to make up to six nesting attempts, but many late-nesting prairie species (scaup, gadwalls and blue-winged teal) may have time or resources to renest only one to three times. Some species like northern pintails are not frequent renesters.