Secret Life of the Spectacled Eider
Study of a threatened duck takes the author and other scientists to the edges of our last frontier and beyond
The temperature outside our twin-engine survey plane was 30 degrees below zero. The overcast sky had merged with an endless expanse of ice, and there was no visible horizon--just white in every direction, as if we were flying inside a light bulb. It was March 1995, and we were over the Bering Sea, 120 miles from the nearest piece of land. We--two U.S. Fish and Wildlife Service biologists and a pilot--were searching for what no one had ever found: where spectacled eiders spend their winters.
As recently as 1992, biologists knew little about these mysterious sea ducks. We did know that some "specs," as we often call them, nested on Alaska's North Slope and in Siberia, but we had no clue how many. We also knew that in the birds' only well-studied nesting location, western Alaska's vast Yukon-Kuskokwim (Y-K) Delta, numbers of specs had plummeted in recent decades. When the species officially was listed as threatened in 1993, a recovery team was formed, and scientists stepped up research to learn about the bird. Some of the main questions in this detective story have been where the birds winter, what has caused the Y-K Delta decline and whether other spec populations also have declined.
On that 1995 flight, in hundreds of miles of jumbled ice, the only signs of life we saw were polar bear tracks. We had one clue for our search: a set of coordinates. Two weeks before we began our survey, a transmitter implanted in an eider had let out a freakish beep. Silent for six months, the transmitter had suddenly come back to life just as my colleague Bill Larned and I were preparing for our search.
Only when our low fuel supply forced us to turn homeward did a curious brown smudge appear on the horizon. We expected it to be perhaps a walrus haul-out site. When the smudge resolved itself into about 500 spectacled eiders crammed into a tiny ice hole, we whooped victoriously. Minutes later, we saw another 50,000 birds packed into a small lead. We flew back to our fuel cache awestruck.
We spent the next day holed up in an Alaska Native village on St. Lawrence Island, watching a blizzard through tightly shut windows. The following day, the plane's heater malfunctioned, and we were grounded again. We were so anxious to return to the eiders that one more delay may have found us walking out to them.
I had to feel sorry for the specs riding out the weather at sea, but I knew they were equipped. The well-insulated, 3-pound birds are sea ducks in the truest sense of the word, spending nearly all their lives riding the waves. The male is on land only about three weeks a year, when he stays close to his mate. Soon after she begins incubating, he heads back to sea, where food likely is more plentiful. Females with broods follow along a few months later. We'd love to know what the birds eat far offshore; our guess is they consume clams or shrimplike invertebrates.
When we took to the air again, we returned to where we had found the flocks. Birds were crammed into tiny holes and cracks in the ice, their only windows to the presumably invertebrate-rich waters below. In three hours, we found two dozen flocks, totaling about 150,000 birds. Surveys in 1996 led to a "wild guess" of a quarter million for the number of wintering eiders, according to biologist Larned. He adds, "All I'd officially say at this point is that we estimate there were at least as many as we saw in 1995."
The flocks were always within about 20 miles of each other. We almost certainly still would be looking for them had it not been for work that took place in a tent on the Y-K Delta the previous summer. There, U.S. Fish and Wildlife Service (FWS) veterinarian Dan MulCahey and biologist Margaret Petersen, then of the National Biological Service, implanted transmitters and battery packs into 26 specs. (That agency is now the U.S. Geological Survey Biological Resource Division.)
The transmitters sent information every few days, and biologists tracked the birds from Anchorage. But their high body temperature unexpectedly shortened the lives of the battery packs, and the radios went silent after a few months. Were it not for the reactivation of one transmitter, the ducks' winter location might still be unknown.
When the spectacled eider was first listed as threatened, the best estimate of its global population was only 50,000. With our team's discovery, the species appeared to be in considerably less danger of going extinct than scientists had thought. Still, eider numbers on the Y-K Delta have declined a shocking 96 percent in the past 25 years. The causes appear to be several pressures on the region's breeding birds.
Waterfowl harvest on the Y-K Delta is difficult to measure. Alaska Native hunting of waterfowl has been, for all practical purposes, unregulated--except in cases of serious conservation problems. However, many Native subsistence hunters do voluntarily report their harvest to FWS. Such reporting by Yup'ik Eskimos on the Y-K Delta indicates they take fewer than 300 specs each year. "Most spectacled eiders are taken incidentally by seal hunters in the spring, before the geese arrive," says Chuck Hunt, Native Liason for the Y-K Delta National Wildlife Refuge. But with the delta's spec population severely depressed, many biologists feel any harvest is unwise.
Due in large part to decades of overhunting at both ends of the flyway, the delta's brant, cackling Canada geese and greater white-fronted geese populations crashed in the mid-1980s. That could not help but disrupt the food web, and waterfowl predators such as the Arctic fox may have begun to prey more heavily on eiders. That idea is conjecture; there are no data to support it. But nearly every one of a dozen experts I have asked has agreed that shifting predator pressure likely has been responsible for some of the eider decline.
On the brighter side, harvest restrictions along the flyway are helping some Y-K Delta goose species rebound. (For more about the Y-K Delta Goose Management Plan and Chuck Hunt's role, see "Saving Geese, Saving Himself," National Wildlife, June/July 1995.) And recent surveys suggest the region's relatively few remaining spectacled eiders may be slowly growing in numbers by a few percent each year.
Another hazard for the birds comes in the form of lead. As in other cases around the world, hunters have unwittingly put tons of lead shotgun pellets where birds can eat them. On the large, remote Y-K Delta, however, the accumulations of lead in permafrost-bottomed wetlands came as a fairly recent surprise to scientists.
Although lead shot was banned nationwide for waterfowl hunting in 1991, understanding of the problem and conversion to steel shot have come slowly to the Y-K Delta. Using available harvest figures and educated assumptions about typical ammunition loads and marksmanship, I have estimated that Y-K Delta subsistence hunters may be putting a minimum of 47,000 pounds of lead pellets into the environment each year. That's 83 million pellets, which waterfowl often mistake for grit that their gizzards use to grind up food. Ingestion of just a few lead pellets can kill a bird--though specs are apparently somewhat more tolerant of lead than other species.
To address the lead-shot problem, the Alaska Department of Fish and Game, Yup'ik leaders and Y-K Delta National Wildlife Refuge staff launched a public-education campaign in recent years to show that non-toxic steel shot is the better way to go. "Once the Natives understand the lead-shot problem," says refuge manager Mike Rearden, "and see for themselves that steel shot is effective, they are happy to cooperate." By March 1998, there will be active enforcement for prohibitions on the use of lead shot on the refuge.
Still, the lead already there will be a problem for many years. At the two Y-K Delta sites that have been studied, federal biologists estimate that a fourth to a third of adult females that come ashore each spring to breed ingest one or more lead pellets before they leave. Of five deaths among 87 radio-marked eiders in the summers of 1993-95, two were due to lead poisoning and a third may have been.
Happily, spectacled eider nesting grounds in Alaska's North Slope and Siberia don't seem to share these pressures. Since 1992, we have found that an apparently stable population of 7,000 to 9,000 pairs of the birds nest on the North Slope. In 1994, surveys by FWS biologists in Siberia discovered that the majority of the world's specs nest along the region's northern fringe. To our limited knowledge, that region has not experienced large-scale changes that could cause the kind of decline seen on the Y-K Delta.
We may never know exactly what caused the eiders' precipitous drop in numbers in western Alaska. Most likely, it was a combination of factors. The species is long-lived and slow to reproduce, so population recovery will take many years. But with luck, perhaps biologists not yet born will fly over the Bering Sea and continue to be blown away by the spectacle of vast wintering eider flocks.
Wildlife biologist Greg Balogh wrote this while sampling life in the lower 48 after 10 years with the U.S. Fish and Wildlife Service in Alaska. He is now back in Alaska.