To Solve the Mallard’s Mysterious Decline, Researchers Turn to Hi-Tech Trackers

Mallards seem to be everywhere. They gather in parks and ponds, forage in farm fields, and even nest in urban planter boxes. This flexibility has helped make Mallards the most common ducks in North America.

And yet, while waterfowl populations overall have grown in the past few decades, Mallard numbers have declined by an estimated 20 percent since 1998, according to annual surveys. In the stretch of the Atlantic Flyway from New Hampshire to Virginia, the losses have been more than twice that. For such an adaptable species to undergo such a precipitous drop is troubling, says John Coluccy, ­director of conservation planning at Ducks Unlimited. “It indicates that something’s going on that we need to be paying attention to.”

In 2021, seeking to understand the trend and find ways to ­reverse it, scientists launched the Atlantic Flyway Migration Project, an expansive research effort spanning 14 states and 3 Canadian provinces. The undertaking is ­ambitious both in its scale—22 government, university, and nonprofit organizations are involved—and in the sheer quantity of information it aims to amass: tens of millions of data points, when all is said and done. “It is truly remarkable,” says Mitch Weegman, a University of Saskatchewan biologist who co-leads the project. “It’s not common that you have several hundred people working on the same problem.”

The goal is to create an extraordinarily detailed picture of Mallard behavior and see how decisions made by individual birds—such as when and where to migrate or build a nest—might contribute to falling reproduction. To do so, the biologists turned to the same behavior-tracking technology many people use to monitor their health. Just as smartwatches help gauge our sleep and trace our daily activity, transmitters ­affixed to the ducks provide ­updates on each bird’s activity every 10 minutes. So far the team has put trackers on nearly 1,200 Mallards, tagging only females to follow their nesting behavior. Weegman says he’s unaware of any other animal study that has netted such a staggering volume of data from so many individuals.

Capturing and tagging all those birds was no small feat—and it was just the first step. Next the scientists had to figure out what the movement data meant. To translate the squiggles and dots from the transmitters into real-life Mallard behaviors, University of Saskatchewan graduate student Cassidy Waldrep used computer models to identify patterns that ­indicate when a tagged bird is flying, feeding, preening, or resting. The team is confident that the models are accurate because they’ve observed tagged Mallards in captivity to ensure that their reading of the data matches the birds’ behavior. In nesting season, they also use a drone with a heat-sensing camera to locate a small sample of tagged Mallards and confirm which transmitter patterns correspond to birds that are actively brooding.

Though it’s too soon to say for certain what is causing the decline, one likely factor has emerged. Daria Sparks, a graduate student at SUNY Brockport, has found that a surprisingly high proportion of the tagged birds don’t migrate. The team is still unpacking the reasons why, but evidence suggests the ­answer might involve genetics. Since the 1940s, sportsmen’s clubs and others have released an estimated 1.8 million farm-raised Mallards for hunting. Today hybrid birds, the result of decades of ­domestic ducks mating with wild ones, make up more than 90 percent of the eastern Mallard population.

What’s concerning are startling differences in behavior between wild and hybrid birds, revealed by 2022 research conducted in the Great Lakes region (which was unrelated to the Atlantic Flyway project). Compared to hybrids, the wild Mallards in that study were less likely to use urban environments, twice as likely to migrate, and three times more likely to incubate a nest. 

“It was pretty eye-opening as to how much those movement behaviors were related to bird genetics,” says Benjamin Luukkonen, a biologist with the Michigan Department of Natural Resources who conducted the research as a graduate student at Michigan State University.

The Atlantic Flyway researchers plan to continue tracking Mallards through 2027, at which point they hope they’ll be able to offer wildlife managers a clearer understanding of how to help the species recover. If birds that breed in rural marshes hatch more chicks than those in suburban parks, for instance, then restoring more wetlands could be a key strategy. Their findings may also help explain why Mallards that breed from Maine north into ­Canada continue to grow in numbers while their neighbors to the south dwindle—a disparity that could hold lessons for conservation.

Sorting out where the problem lies is only becoming more urgent. Buoyed by expanded wetland protections, ducks had been a recent bright spot amid otherwise dismal avian population trends in the United States. But the latest “State of the Birds” report, published in March by a coalition of science and conservation groups, including Audubon, showed that duck populations have declined significantly in the past few years—a reversal likely due in large part to drought in the Prairie Pothole Region of the northern Great Plains, where millions of them breed.

As scientists and conservationists seek ways to help Mallards and other waterfowl rebound, the vast trove of data from the Atlantic Flyway project could prove invaluable, Coluccy says. “It’s going to be mined for a very long time.”

This story originally ran in the Summer 2025 issue as “Mallards in Motion.” To receive our print magazine, become a member by making a donation today.

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