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Black Ducks in Peril

The Atlantic Flyway’s most iconic bird has dwindled to less than half its historic population. Will new research turn the tide?

2/28/2013

Any Audubon wannabe can appreciate the obvious beauty of a wood duck, pintail or redhead while gazing through a binocular, but the American black duck is different. It has a subtle splendor to it, lovely as it is, that requires more than casual observation. Every time I’m fortunate enough to carefully admire one, close up, in my hands, its breast seems a bit deeper chocolate; its violet-blue speculum a tad more iridescent; the undersides of its wings an even more perfect shade of white. Such understated good looks do however seem befitting of the black duck. He doesn’t crave attention, being less social than more gaudy-colored ducks. And due to this nature, along with his instinct and cunning, he requires careful coaxing to the decoys. The hunter who bags but one duck—as long as it’s a black—can return home satisfied.

For these reasons the black duck is the most iconic bird of the Atlantic Flyway, arguably defining the region it predominately inhabits more than any duck anywhere else. How tragic it would be for an entire waterfowling culture if we were to lose it. And yet, black ducks are in trouble.

While historically they heavily outnumbered Eastern mallards as far west as Wisconsin, they began to decline steadily in 1950 and are no longer even counted in the Mississippi Flyway’s population survey. Currently only the Atlantic Flyway offers a reasonable expectation of bagging one and, while mallards have expanded their breeding range, less than half the black duck population exists as when Columbus arrived.

The U.S. Fish and Wildlife Service’s 2012 breeding population survey estimate was 603,100 black ducks, 27 percent below the North American Waterfowl Management Plan’s goal of 830,000 and 3 percent below the long-term average (based on survey data collected since 1990) of 622,000.

So, what’s killing the black duck, and what can be done? Here are the myths, theories and the latest research seeking to answer those very questions.

Why the Decline?
Ducks Numbers“Unfortunately there’s just no silver bullet answer to why black ducks are declining,” explains John Coluccy, Ducks Unlimited’s (DU) black duck research coordinator. “There are a host of potential variables, but, based on our research, we believe the carrying capacity of the habitat is the primary factor limiting the black duck population.”

Unlike mallards, black ducks are almost exclusively carnivorous as they head south, feeding on high-protein invertebrates such as killifish, fiddler crabs, snails and other invertebrates. While black ducks are found in a variety of environments, they prefer to feed in salt marsh mud flats, which most consistently provide an ample, stable supply of their favorite foods.

Unfortunately, in the 1930s about 90 percent of Atlantic coastal marshes were grid-ditched (drained) to prevent the proliferation of mosquitoes. Can it be mere coincidence that the destruction of this habitat and the food resources it provided was a precursor to the black duck’s decline?

DU believes not, which is why a key component of its black duck management plan includes the protection and restoration of coastal marshes. As part of its partnership with the Black Duck Joint Venture, a program established with the goal of restoring the black duck population to 640,000 birds, DU has begun working with mosquito managers to restore tidal flow to coastal marshes.

“We assume we will improve the habitat for black ducks, see more of them and note more of their preferred foods,” says Coluccy. DU’s latest study with the Black Duck Joint Venture seeks to quantify that assumption. Biologists are restoring salt marsh habitat at the Silver Sands State Park, a major black duck wintering area along the Connecticut coast, and will compare it to non-restored sites over the course of four years.

“It could have big ramifications for the future of black duck management,” Coluccy says. “If we find that black ducks thrive in the restored coastal marsh habitat then it indicates the impact a large-scale restoration in key wintering areas could have on the black duck population.”

Are Mallards to Blame?
If you’ve shot mallards and you’ve shot black ducks, then whether you realize it you’ve likely shot a mallard/black duck hybrid. Doesn’t it stand to reason, then, that mallards—aggressive-breeding ducks that have expanded well east of their historic spring nesting range—are outcompeting black duck drakes for their hens?

“Hybridization of black ducks is becoming a larger issue,” Coluccy says. “Blacks and mallards were once geographically isolated, but now we’re seeing increasing overlap in the breeding areas and almost complete overlap in the wintering areas. The opportunity is there for mixed pairing. We are tracking the rate that’s occurring with winter banding, recording hybrids and things along those lines.”

Research by DU provides some indication that mallards are more aggressive in their quest for hens, outcompeting the milder-mannered black duck drakes. They also may outcompete black ducks for food resources and real estate, forcing them to move to less desirable locations.

At one time some biologists believed black duck hens even preferred the more brightly colored mallard drakes, but that proved to be false. In fact, black duck hens may not willingly mate with mallard drakes at all.

“My personal thought,” says Frank Rowher, scientific director for Delta Waterfowl, “is that the hybrids are a result of forced copulations on the breeding grounds. I don’t think mallards and blacks actually pair on the wintering grounds, as some have suggested.”

Rohwer bases this theory on research conducted when he was on the faculty at the University of Maryland.

“This was back when private groups and even the state were doing a lot of big mallard releases, and we thought this could be adding to the hybridization,” says Rohwer. “So in January and February, when you expect to see paired ducks, we searched the Blackwater National Wildlife Refuge and a variety of big private lands for mixed pairings—and I mean we looked hard—but we couldn’t find a single one. And maybe that makes sense, because mallards and blacks have always wintered together in huge numbers on the Chesapeake Bay for example, but hybridization is a relatively recent problem.”

What can be done to stop the hybridization and spread of mallards east into black duck strongholds? Probably very little. Mallards are the whitetail deer of the waterfowl world: extremely adaptable, hearty and more than willing to expand their range.

“Mallards are such generalists,” Coluccy notes. “But black ducks are just wired a little differently. I’ve been around both species in captivity, and black ducks are a lot more temperamental and sensitive to change. That’s again why protecting habitat is our focus at DU.”

Habitat may even be nature’s way of preventing black/mallard hybrids.

“You don’t see mallards and other dabblers foraging in salt marsh habitats,” says Coluccy. “That’s a critical difference between them and black ducks. So, when salt marsh habitat is lost, not only does it mean less food, less carrying capacity for black ducks, but it could force them to interact more with mallards. If we provide quality salt marsh habitat, we can better ensure separation between species.”

Agriculture’s Effect
Another point of debate in the mallard/black issue is whether it’s primarily agriculture—not mallards—that has interfered with breeding black ducks. Given the sensitivity of black ducks to disturbance, could farming have forced them out and paved the way for mallards to move in?

“That very well could be the case,” Coluccy says. “There’s still a stronghold of black ducks in undisturbed regions, such as the boreal forests of northern Ontario, Quebec and maritime provinces to the east. That’s now the core breeding range, and where the highest densities are being recorded. A big focus of DU-Canada is in trying to secure those unindustrialized areas to prevent development.”

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