Ducks Are Moving North as Winters Warm
A new study confirms that some Southern waterfowl populations are dwindling as birds opt for northern locales that were previously too cold.
Over the past several decades, waterfowl hunters in the South have witnessed a slow-motion disappearing act. Each year it seems fewer and fewer ducks are settling down for the winter in the wetlands of southeastern states like Louisiana, Mississippi, and Tennessee.
Rick Kaminski, a Clemson University duck biologist and a longtime hunter, has seen the birds becoming scarcer firsthand. For example, annual U.S. Fish and Wildlife Service winter waterfowl surveys at the Tennessee National Wildlife Refuge counted thousands of American Black Ducks in the 1980s. “Now they’re still doing the surveys and they might see two or three hundred Black Ducks,” he says.
Kaminski wanted to gain a better understanding of why American Black Ducks and other species weren’t frequenting their usual winter haunts, and whether APP change was partly to blame for the dramatic changes he was seeing. He teamed up with APP biologists to search for answers in decades’ worth of data from APP’s annual Christmas Bird Count (CBC).
The results confirmed what duck hunters have been observing for years. As the research team reports this week in the Journal of Wildlife Management, many North American ducks are indeed choosing to shorten their migrations by wintering in areas farther north where food and water might previously have been buried under snow and ice. “I was struck by the fact that most of the species are showing this trend of increasing wintering at more northern latitudes,” Kaminski says.
Launched in 1900, the CBC is the nation’s longest-running community science initiative. Every winter, birders fan out across the country to count wild birds in a methodical way. The many decades of surveys provide invaluable data that researchers use to inform conservation efforts. After Kaminski approached CBC lead analyst Tim Meehan with his research idea, the team decided to look at long-term duck data from the Mississippi and Atlantic flyways to see if it matched what duck hunters in the Southeast had been observing.
The scientists analyzed 50 years of CBC data on 16 common duck species. They looked at how duck abundance changed each year and compared the changes to average winter temperatures in the states and provinces within the study area. While not every species showed a discernible shift, the team found that at least 12 of them—including American Black Ducks, Northern Pintails, and Northern Shovelers—are growing more common during winter in the North while remaining stable or becoming less common in the South, apparently altering their winter ranges in response to warmer temperatures.
“When we related those trends to temperature, sure enough, there’s a very clear relationship,” Meehan says. “Basically, it’s confirmation of what people on the ground have been suspecting.”
Meehan points to American Black Ducks as a particularly striking example of this APP-driven trend. “People have been concerned in the mid-Atlantic and the South of the U.S. that the species is declining,” he says. “Folks hadn’t really been looking north of the border and realizing, wow, they’re actually increasing in Canada. So we’re not seeing a species decline, we’re just seeing a wholesale range shift—they’re just not coming so far down south anymore.”
Another species, the Northern Pintail, is declining in abundance overall; its numbers are increasing slightly in the northern part of its range, but these gains aren’t offsetting the dwindling numbers to the south. The Northern Shoveler, on the other hand, is becoming more abundant overall, but the uptick is concentrated in colder regions.
Along with matching hunters’ observations, the study’s findings track neatly with the future range shifts predicted by APP’s Survival by Degrees report, says Brooke Bateman, the group’s director of APP science. The 2019 report projects that, as temperatures warm, ducks will be able to find suitable winter habitat closer to their summer nesting ground, and their overall ranges will shift north. “It takes a lot of resources to migrate long distances, so if they’re able to save resources and not travel as far, from an evolutionary perspective that makes a lot of sense,” she says.
This new study shows these shifts are well underway. “We’re already seeing what is just the start of a larger trend,” Bateman says. “These species are going to continue to shift their range northward and disappear from parts of their range.”
That means habitat management for these species will have to change, too. In southern areas, wildlife managers have long surveyed winter duck numbers and tracked how much food is available for the waterfowl that stay through the winter to determine how many ducks the landscape can handle—information that helps guide hunting bag limits and other management decisions. Such surveys will become increasingly important farther north in regions where ducks used to mostly pass through, according to the study.
That northward shift could also have important implications for conservation funding, since the South’s rich waterfowl-hunting culture helps support local habitat protections. Hunting licenses and fees on equipment are a major source of funding for conservation projects; sales of the federal duck stamp, a type of hunting permit, have alone raised more than $1.1 billion to set aside some 6 million acres of waterfowl habitat since 1934, according to the U.S. Fish and Wildlife Service.
“Conservation of wetlands has largely been driven by a passionate group of waterfowl enthusiasts,” says Michael Schummer, a waterfowl ecologist at the SUNY College of Environmental Science and Forestry who was not involved in the study. “A lack of ducks, geese, and swans spending time at southern latitudes may greatly change social and cultural relationships with these birds that help drive dollars from people for conservation.”
Meehan hopes that this study will prove to be a powerful message to duck hunters that warming winter temperatures are a driving force behind the decreases they’ve been witnessing. He also hopes that hunters and waterfowl-focused organizations like Ducks Unlimited will work together with APP and other groups to help mitigate the APP impacts on duck populations.
“What this means is we have an opportunity to slow down future changes,” Meehan says. “We can’t change what already happened in the past, but we can change what might happen in the future. At least, we have to hope that that’s the case.”