By BOB FRYE / Everybody Adventures
This is a mystery playing out in the green-headed, web-footed form of the commonplace, the familiar, the normal.
That only makes it all the more confounding.
Mallards are the everyman’s duck. Scientists say their survival strategy is more “elastic” than that of other waterfowl species, meaning they need no special habitat, no special conditions, to thrive.
“Mallards will find a way to get it done just about anywhere,” said John Devney, vice president of U.S. policy for Delta Waterfowl, a hunting conservation group.
That generalist lifestyle has long served them well in the Atlantic Flyway, the bird migration route that follows the East Coast from Florida into eastern Canada.
They’re not a native species, said Jim Feaga, a regional biologist with Ducks Unlimited, another hunter conservation organization. In Colonial times, black ducks dominated the flyway. Mallards showed up later.
Some emigrated from the Midwest as habitat and agricultural practices changed. Others, Feaga said, were imported from Europe for hunt clubs.
All adapted quickly and well.
“They’re pretty much everywhere now,” Feaga said.
That’s been a boon for waterfowlers. Mallards are the most commonly harvested species in the flyway and have been since the late 1970s, said Joshua Stiller, waterfowl biologist for the New York Department of Environmental Conservation.
They remain relatively abundant, too.
The flyway draws its mallards from two sources: a breeding population in eastern Canada and another in the northeastern United States, Devney said.
The total population of ducks, combining the two, stands at about one million, Stiller said.
“It’s not like mallards are going to go extinct any time soon,” said Ian Gregg, game management division chief for the Pennsylvania Game Commission. “They’re still the most abundant duck in the harvest and overall population.”
And yet, something troubling is going on.
While the eastern Canada mallard population is stable, the northeastern United States one is on a long, downward spiral. It’s shrunk 20 percent since 1998, Stiller said.
The question is why.
Ducks fly across state lines. So when it comes to waterfowl management, the Atlantic Flyway Council — made up of wildlife managers in 17 states, six Canadian provinces, one Canadian territory, Puerto Rico and the U.S. Virgin Islands – establishes season lengths and harvest limits.
It determines how many days of duck hunting a state can offer, for example. The state then slots them into the calendar as it sees fit.
What’s noteworthy is that starting in 1997, the Flyway Council liberalized seasons. Hunting days went from 45 to 60, with a daily limit of four mallards, no more than two of which can be hens. That remains the way things are today.
Mallard populations were growing until then; they’ve declined annually ever since, Gregg said.
That’s not entirely a shock, Stiller said.
“It’s worth noting that all of our population models that we’ve used to date suggest that we are slightly overharvesting mallards at the current rate,” he said.
But it may not be entirely accurate to blame hunting alone for the mallards’ troubles.
“Now, there’s obviously correlation. That doesn’t mean cause and effect,” Gregg said.
The Flyway Council has a mechanism for monitoring mallard numbers, Devney said. It’s based on what he called the “world’s most simple population model.”
Each spring, working from planes and on the ground, scientists estimate mallard populations. To that they add recruitment, i.e. the total of ducklings born.
They also calculate hunter harvest by putting leg bands on a certain number of ducks, then seeing what percentage are reported killed.
The resulting number – population plus recruitment minus harvest — is compared year to year to track trends.
Right now, Devney added, there’s nothing in that model to suggest mallards should be in trouble. And yet there’s no denying populations are shrinking, he admitted.
That’s the mystery.
“Based on what we see from band return data, survival has not declined. And based on what we see in the age ratio data, production has not declined,” Devney said.
“So if your survival is constant, and your production is constant, it’s hard to understand why we’re having this declining population. Frankly, I don’t think anybody’s got a good answer for how one plus one equals six.”
His guess is that one of those data sets has a “bias,” meaning it’s providing bad information. Harvest might be underestimated or survival overestimated.
What’s clear is that changes are coming.
Duck season lengths in 2018-19 will continue as they have been, per the Flyway Council. They’ll likely stay the same in 2019-20.
Hunters value opportunity – the chance to get outdoors — over anything else, including birds in hand, so the plan is to maintain season lengths, Stiller said.
But mallard harvest limits are expected to go from four per day to two. They’ll likely stay there for a period of years, though no one knows how many.
“What you do is start with harvest, to see if reducing harvest pressure produces a response from the population. Because that’s the one thing you can control,” Stiller said.
In the meantime, some other research into the mallards’ woes is underway.
Scientists in Texas are looking at mallard DNA to determine any “Old World” influence. There’s some thinking, Feaga said, that Atlantic Flyway birds descended from European imports might differ genetically from birds of wild stock in ways that make them less able to compete and survive.
Others are looking at habitat.
There are no obvious changes that bode ill for mallards, Devney said. If anything, he said, the rate of wetland loss has slowed in recent decades.
And no other ducks are struggling the way mallards are, as might be expected if there was a problem with living conditions.
“But maybe there’s something going on that we’re just not queing in on,” he said.
Still others are examining whether mallard populations are settling in at a new normal.
For years across the northeast, state wildlife agencies trapped turkeys from places where they had a lot and moved them to places without any. Populations exploded.
More recently, flocks have contracted to match the carrying capacity of available habitat.
Some speculate mallards might likewise be finding their own “equilibrium,” Feaga said.
“The hope is that they re-stabilize at some population’” Stiller added. “It may be lower than what we historically had. But as long as it stabilizes, that will be ok.
“The concern right now is that it’s not stabilizing, it’s just continuing to go down.”
So the mallard mystery continues. And what’s next for the ducks is uncertain.
“That’s a pretty good question,” Feaga said. “And I don’t know that anyone has the answer to that yet.”