Bay Journal

Scientists diving into secrets of elusive seaducks

  • By Karl Blankenship on January 01, 2004
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Researchers can place different foods in the sediment on the bottom of a 12-foot-tall dive tank, then watch through windows as the ducks dive, to see what they chose to eat. (Fred Greenslade / Delta Waterfowl ) An implanted radio transmitter—which left a short antenna sticking out the back of the this surf scoter—will allow the bird to be tracked by satellite. (U.S. Geological Survey)

Last summer, a group of ducks led some Bay scientists on a wild goose chase. Tipped off that a group of surf scoters were nesting on a lake in Labrador, Canada, a research team headed north.

They searched the area with a helicopter, they hired a guide with trained dogs—they even got help from people at a nearby NATO base.

They crawled through forest underbrush in densely vegetated roadless areas, swatting mosquitoes every foot of the way. But in the end, the team of scientists from the U.S. Geological Survey’s Patuxent Wildlife Research Center never found a nest.

“It’s very much like trying to find a needle in a haystack,” said Alicia Wells, one of the scientists involved. “I had tons of people out there with me. We found five females on five different ponds, but they never even once acted like they were nesting.”

Such frustrations are one of the reasons why seaducks, such as the surf scoter, are the most poorly studied waterfowl of North America. One thing is known: “The long-term trend is the species are declining,” said Matt Perry, a research biologist who is leading the center’s seaduck effort.

That’s true for the Chesapeake Bay, one of the most important wintering areas for the birds, as well as for many other populations. The reason, like the answer to many questions about seaducks, comes in three words: No one knows.

Suspects in the decline include degraded water quality in the Bay and other wintering areas, disturbances in their summer nesting grounds, increased hunting pressure—or all of the above.

But no one knows. The 15 species of seaducks—that’s 42 percent of all duck species—are so poorly studied that much about them remains a mystery even as other waterfowl have been studied for a century.

When the authoritative book,“Ducks, Geese and Swans of North America,” was published in 1980, everything known about surf scoter nesting was based on a single study of one nest. “You come across those kinds of things and it’s just hard to believe,” Perry said.

Part of the lack of interest stems from the fact that seaducks historically were not a main target of hunters. “They don’t taste good,” Perry noted. Most attention went to waterfowl that had more recreational value.

Further, seaducks are particularly hard to study. They get their name because they stay a mile or more out in the water, where they are hard to find. And because they are darker than many other birds, they are hard to see during aerial surveys compared to other, lighter, duck species. “When you fly over them, and they are relatively scattered over a large area of water, they just disappear,” Perry said.

Compounding those problems is that the birds nest over huge areas of Canada and Alaska. Nests are widely scattered in roadless areas. Researchers have to fly into areas and literally crawl through brush so dense they could easily overlook a nest only a few feet away.

“A whole team will spend weeks searching for nests and maybe find one,” Perry said. Black scoters have been particularly difficult—none of the scientists has even seen one of their nests yet.

Things are beginning to change, in part as a result of the 1989 Exxon Valdez disaster in Alaska, which left a huge number of seaducks soaked in oil. Because no one knew much about the birds, scientists had trouble quantifying how important the disaster was to the overall population. “If a judge asks you what a duck is worth,” Perry noted, “you need to know how to answer.”

Research has been stepped up since then, culminating in the creation of a formal joint venture between Canadian and American managers and scientists in 1998. The Patuxent scientists, whose work is being funded by the U.S. Fish and Wildlife Service, U.S. Geological Survey and the Sea Duck Joint Venture are one of the key research teams in the effort, and are focusing on birds using the hugely important Chesapeake Bay.

Although seaducks spend their winters anywhere along a 2,000-mile range from Labrador to Florida, it’s estimated that between a quarter and a third of the entire Atlantic Flyway population is concentrated in the Bay.

The Chesapeake has eight seaduck species, but researchers are focusing on the four which are least studied: the black scoter, surf scoter, white-winged scoter and the long-tailed duck (formerly known as the oldsquaw).

Although those birds winter in the Bay, no one actually knew where the birds were spending their summer breeding seasons. To find out, the scientists in recent years have tried various techniques to capture live ducks on the Bay so they could be implanted with transmitters and tracked.

Catching the birds is no easy task. The scientists tried various techniques, such as chasing seaducks in speeding boats while firing a net from a specially designed gun. What they learned, Perry said, is that the ducks are difficult to catch, although Perry’s team has captured 23 surf scoters. No black scoter has ever been successfully caught in the Chesapeake, despite weeks of effort, because of their low numbers.

To tag that species, the scientists finally had to go to the Restigouche River in New Brunswick, where the birds congregate during migration in total flocks of nearly 100,000 ducks. There, teams of Canadian and American scientists would use nightlighting techniques to daze the ducks and capture them.

Radio transmitters were implanted—leaving a short antenna sticking out the back of the ducks—which allows the birds to be tracked by satellite. It’s expensive: the transmitter, and the cost of the satellite data, adds up to about $5,000 a bird.

But it is revealing new information about the birds’ migration routes, important staging areas for migration and—most importantly—where they are nesting.

The transmitters also give the scientists an important edge in finding nests in the wilderness. “These birds nest in dense, woody vegetation,” Perry said. “To get through, you have to get down on your hands and knees and crawl.” Using hand-held tracking devices, they can find the nests and determine what types of habitat the birds are using.

In some cases, they are also swiping some eggs. The eggs, usually from abandoned nests, are put in incubators and brought back to the Patuxent Center, where scientists are rearing a colony to study in captivity so they can better understand their diet in the Bay.

One thing that tracking has shown, Perry said, is that the birds return to the same location each winter. “They come back because they know where the groceries are.”

It’s possible, though, that the groceries in the Bay have changed because of poor water quality. Because they live far from shore, seaducks find their food by diving 20–40 feet to the bottom and rooting around for clams, mussels and other bottom-dwelling creatures in deep habitats that have been affected by low-oxygen conditions in recent decades.

As part of the seaduck effort, scientists at the Patuxent Center have launched a multiyear effort to learn what the birds are eating in the Bay, whether that is changing, and whether it is providing an adequate diet.

After examining hundreds of gizzards and gullets from seaducks obtained from hunters in the past few years, Patuxent researchers have already learned that the birds are eating, for the most part, hooked mussels, although they consume large numbers of dwarf clams, gem clams, and a variety of other bottom dwellers.

“The diversity of species found in ducks from the Chesapeake, compared with those from other areas, shows how extremely important estuaries are,” said Peter Osenton, who is overseeing the analysis.

He and his assistants peer through telescopes at bits of shell extracted from the ducks, and compare them with a “reference” collection of shell fragments.

But it’s not clear whether what is found in their gullets and gizzards is the most nutritious, and preferred, diet for the ducks. It also doesn’t tell scientists how hard the ducks had to work to get their dinner.

That’s where the captive colony comes in. Surf scoters and white-winged scoters are being kept in pens at the research center—scientists are still trying to track down eggs from black scoters and long-tailed ducks, the latter of which breed in hard-to-reach areas near the Arctic Circle. Those birds are being fed different mixes of feed and carefully examined to determine their ideal diet.

The scientists will then test the birds in a 12-foot-tall concrete dive tank. Researchers can place different foods in the sediment on the bottom, then watch through windows as the ducks dive, to see what they chose to eat.
Through careful studies and blood analysis, they can determine the nutritional value of different food types, as well as the amount of energy the ducks spend diving to find it. It’s possible that subtle changes, such as the type of amino acids found in different clams, is affecting the energy levels of the ducks, said Alicia Wells, who is overseeing the nutritional studies.

David Kidwell, who is overseeing benthic surveys for the project, said chronic low-oxygen conditions during the summer in feeding areas “could have any number of implications” for duck diets. It may alter the amount, or variety, of clams and other bottom-dwelling creatures. Or, it might be limiting the size of clams—in effect forcing the ducks to spend energy diving, but getting less food for their effort.

By comparing the abundance of what’s on the bottom to what is found in the gizzards and gullets of wild ducks, the scientists can also determine how selective the ducks are in feeding. If one item accounts for only a small fraction of what’s on the bottom, but accounts for much of what the ducks are eating, it may show they are highly selective for certain things.

In key feeding areas, Kidwell also plans to survey the bottom areas before and after the ducks’ wintering season to see how much the birds are eating. If, for instance, the spring surveys show the clam beds—or the sizes and species needed by the ducks—have become greatly depleted since the fall, it may show that the Bay is barely producing enough for the ducks to eat.

“We are trying to figure out what has gone on in the Bay, and how it affects seaducks, so we can make sure that they don’t keep declining,” Wells said.

(Improving bottom habitats used by feeding seaducks was one of the goals of new dissolved oxygen water quality criteria developed by the Bay Program last year.)

The notion that poor water quality in the Bay could affect waterfowl abundance is not unprecedented. Past work at Patuxent by Perry and others showed that water quality changes dramatically affected the diet of the canvasbacks, once the most abundant duck on the Bay.

The canvasbacks once primarily fed on underwater grasses during the winter, but as the beds declined, the ducks were forced to switch their diet to clams, which are much less nutritious. That has contributed to a sharp decline in canvasbacks in recent decades.

Other issues, such as increased boat traffic, which disturbs resting birds, may come into play as well. Every time the birds take off, they burn energy—which means they have to make more dives for more food.

But potential problems aren’t limited to the Chesapeake.

As hunting restrictions increased in recent decades to protect other waterfowl populations, it’s thought that hunting pressure began to increase on seaducks.

No one knows how extensive the seaduck harvest is.

At the other end of the range—on the summer breeding grounds in northern Canada—the ducks are also used by Inuits and other Native Americans who live off the land. No one knows the extent of their take, either.

Some of the breeding areas have massive hydroelectric projects, which flood vast areas, and huge logging or mining operations. “They are impacting huge amounts of land,” Perry said. “There is no doubt about it. But nobody really knows how big of an effect it is having, and some could argue that flooding some of these areas for hydroelectric power may increase habitat.”

Another factor, Perry said, could be the slowly increasing access to lakes in northern Canada to fishermen. As lakes are increasingly visited, some people often introduce prized species such as northern pike, which are duckling predators, into waters that had once provided a safe haven.

“We’ll drive hour after hour and see all these lakes that look wonderful,” Perry said. “but there are no ducks on them.”

Any, or all, of those factors can add up to take a toll. Most seaducks do not mature until they are 2 or 3 years old, and the number of young that survive tends to be low compared to other duck species. That makes their populations susceptible to any increased source of mortality.

“We’re getting little pieces of the puzzle,” Perry said. “but to say there is one simple answer that affects the population, that’s unlikely.”

But with luck, fewer wild goose chases, and a bit more time, it’s likely that fewer questions about seaducks will be answered with, “no one knows.”

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About Karl Blankenship

Karl Blankenship is editor of the Bay Journal and executive director of Chesapeake Media Service. He has served as editor of the Bay Journal since its inception in 1991. .(JavaScript must be enabled to view this email address).

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