Researchers used satellites to reveal spectacled eiders’ secret
|A pair of spectacled eiders (male on left, female on right) rest on the ice on Alaska’s North Slope in June 2006.|
Nesting only in coastal Alaska and Russia, spectacled eiders are truly Arctic birds, toughing out the winter months in conditions that make “Deadliest Catch” TV episodes look like a cruise vacation.
Outside of the brief Arctic summer, spectacled eiders live so remotely that their winter whereabouts were a mystery until the mid-1990s. They were one of the last North American species to hold such secrets.
In Alaska, spectacled eiders nest only on the North Slope and the Yukon-Kuskokwim Delta in Western Alaska.
Solving the puzzle of where the birds vanished in winter became urgent when a 1992 survey showed the Y-K Delta population had plummeted from about 50,000 nesting pairs in the 1970s to fewer than 2,000 pairs. The cause of the alarming decline was unknown. It earned the spectacled eider a place as a threatened species on the U.S. Fish and Wildlife Service’s Endangered Species list in 1993.
Researchers suspected the eiders wintered somewhere on the Bering Sea, but aerial surveys in winter were risky and expensive without knowing where to start.
|A male spectacled eider [LEFT] flies above a lake on Alaska’s North Slope in June 2007.
Signals From the Sky
From 1993 to 1996, U.S. Fish and Wildlife Service biologist Margaret Peterson and her team tried something new: implanting transmitters powerful enough to send location signals to satellites orbiting the Earth. It was the first time anyone used satellite tracking with birds as small as eiders. Researchers could monitor locations of tagged birds on a computer and use those locations as starting points for aerial surveys.
In March 1995, an unexpected late-winter signal from a transmitter that had been silent for months had U.S. Fish and Wildlife Service biologists Greg Balogh and Bill Larned flying far out over the dark, frozen Bering Sea. There was the possibility the signal was a malfunction, but they had to check. The temperature was about 20 below, and they had to charter a burly twin-engine plane to carry them over the vast expanse of ice.
“We spotted a smudge on the ice, and we thought it was walrus hauled out,” Balogh said.
Safe in Numbers
That smudge turned out to be a flock of spectacled eiders. The first flock they saw numbered about 500. The next view was unbelievable: 50,000 birds. The biologists were ecstatic.
“Nearly every crack in the ice had a flock of eiders; they were basically keeping the ice open like a big eiderdown blanket on the ocean,” Balogh said.
Later surveys documented 370,000 spectacled eiders.
This species is unique among eiders: the entire world population huddles in one place for the winter, south of St. Lawrence Island in the northern Bering Sea. Such a gathering also means spectacled eiders are vulnerable to natural or human-caused disturbance.
The region around St. Lawrence Island draws the eiders for two reasons: patches of open water in the sea ice (called “polynyas”, pronounced pahl-in-YUHS), and all-you-can-eat food. Usually, winds from the north push ice south through the Bering Strait until it piles up on St. Lawrence’s north side. Like a linebacker plowing an open path, St. Lawrence blocks some of the ice, which piles up on the island’s north side, creating an “ice shadow” on the south side. Spectacled eiders flock together in the resulting polynyas. Russian currents sweep nutrients into the relatively shallow area (about 130 feet deep), supporting a vast sushi bar. Spectacled eiders are excellent divers; they plunge to the bottom to root around for half-inch clams and small marine worms to swallow whole. The ice constantly changes, drifting over new patches of sea bottom with a fresh supply of clams.
A newer study, started in 2008 by Matthew Sexson of the U.S. Geological Survey’s Alaska Science Center in Anchorage, delves deeper into eider migrations using today’s improved technology. Longer-lasting transmitter batteries deliver information for up to two years instead of a few months. The 1990s study had about 200 eider locations beamed up; Sexson’s study has nearly 10,000.
The Bird Dance
Spectacled eiders have another winter pursuit: finding next season’s mate. “As spring develops it turns into this big cocktail party,” Sexson said. By looking at a combination of satellite data and genetic samples, his study has shown an interesting split in the travel agendas between male and female spectacled eiders.
Some genetic information shows there are distinct populations of females in Russia, the Alaska North Slope and the Y-K Delta, which means females tend to return for nesting to the place where they grew up. Other genetic information shows there isn’t a geographic distinction between males — they may travel between all three breeding areas.
The satellite locations support this. The vast majority of the world’s spectacled eiders nest in Arctic Russia. The satellite locations showed males tagged in Alaska sometimes breed in Russia the next season if they hook up with a winsome Russian gal (the odds are high that a female they meet is Russian). Alaska females are adamant about taking a new guy to their place for a romantic rendezvous.
One mystery the last 20 years of research hasn’t solved is what caused the chilling drop in the number of Y-K Delta birds. It’s probably a combination: birds dying from eating spent lead shot from hunters, predators such as foxes and gulls eating more eiders due to declining populations of other waterfowl species and shifting temperatures and currents in the marine environment that affected the winter food supply.
While we may never know exactly what happened, it’s encouraging that the Y-K Delta population has been slowly but steadily increasing. Not allowing hunting of spectacled eiders and a ban on lead shot may have helped. There are now roughly 10,000-12,000 birds on the Y-K Delta, and the same number on the North Slope. “I’ve been working with spectacled eiders on the Y-K Delta for 10 years,” says Julian Fischer, a migratory bird biologist with the U.S. Fish and Wildlife Service. “It’s great to see them—I now see them much more often than I did 10 years ago.”
The information researchers continue to uncover about where these hardy Arctic birds live is increasingly important as new challenges emerge. With diminishing sea ice, shipping and fishing are growing in the Bering Sea and farther north. There is also the prospect of oil or gas development farther north and on the eiders’ North Slope breeding grounds. Knowledge of the places these birds need to survive will be a valuable tool to ensure the world’s spectacled eiders continue to exist in the windswept, groaning sea ice as they have for untold centuries of winters.
Beth Peluso serves as communications manager for Audubon Alaska, an organization that promotes science-based conservation to protect important habitat for birds and wildlife across Alaska. Learn more about Alaska’s amazing birds at www.AudubonAlaska.org.