Spectacled Eider Wintering Grounds Found
In March 1995, while Wildlife
Biologists Greg Balogh and Bill Larned were searching the Bering Sea pack ice
for the never-before-found wintering grounds of the spectacled eider, they made
a dramatic discovery. Huge, dense flocks of spectacled eiders sat scattered beneath them, crammed into small holes in the ice, holes kept open
in the -20 degree F weather by the heat and movement of the birds themselves.
Most of the world's threatened spectacled eiders (Somateria fischeri)
fly to northern Russia to breed. Smaller portions of the world population fly
to Alaska's Arctic Coastal Plain and Yukon-Kuskokwim Delta to nest. Although there
is no population trend information for this species in Russia, traditional knowledge
of Alaska North Slope Natives suggests that breeding populations of this species
have declined notably on Alaska's Coastal Plain. Data from U.S. Fish and Wildlife
Service spring waterfowl breeding surveys suggest a dramatic decline of over 90%
on the Yukon-Kuskokwim Delta during the past forty years.
The species has
long been studied on its breeding grounds, but what the birds did with their time
during the winter was one of the last great mysteries to waterfowl biologists.
It seemed that the birds just disappeared out to sea each summer and autumn, returning
to their breeding grounds come spring.
Then, in March 1995, Fish and Wildlife Service biologists
Greg Balogh and Bill Larned, with the technical support of National Biological
Service Biologist Margaret Petersen, finally unlocked the mystery. On the trail
of a freak signal from a long silent satellite transmitter, they found nearly
150,000 spectacled eiders (roughly equal to the current world-wide breeding population
estimate) rafted in an otherwise unbroken sea of ice halfway between St. Lawrence
and St. Matthew islands in the Bering Sea. Over 2 dozen eider flocks were all
within about 20 miles of each other. There were no other signs of life above the
ice except for a lone walrus and one presumably well-fed snowy owl.
Arctic version of the monarch butterflies wintering in the Sierra Madre Occidentale,
the eiders were packed tightly, body to body, head to tail, into small holes in
the ice. The flocks were so incredibly dense that the biologists felt their camera
equipment could not adequately record the flocks for an accurate count off of
photos. Their estimates of flock size, they realized, were nothing more than best
Given the -20 degree F temperatures that reigned over the area
during the previous weeks, these holes were presumably maintained as open water
solely by the activity of the birds themselves. When one flock that was startled
by the aircraft lifted into the air, a dense cloud of steam poured off the water
until the birds once again settled into the only spot of open water within sight.
New leads forming in the shifting ice were frozen over in minutes.
survey a few weeks later found the eider flocks in the same place. Warmer temperatures
prior to this second survey resulted in more open water and less congested flocks
than were present on the previous survey. The looser groupings of birds made counting
them on photos much easier. The 155,000 bird estimate actually came from this
Eider Implants Critical to Investigation
it not for electronic miniaturization, this icy mystery would likely have continued
for years. But with the advent of satellite transmitters and battery packs lightweight
enough to be carried by spectacled eiders, the species's secrets have begun to
thaw. From May 16 to June 1, 1994, biologist Margaret Petersen and veterinarian
Dan Mulcahy implanted satellite transmitters and battery packs into 22 spectacled
eiders from the Yukon- Kuskokwim Delta. The antennae protruded from the birds
body cavities through their skin via a tiny grommet.
Petersen had the implanted
satellite transmitters programmed to send out signals in 6-hour bursts once every
three days. Transmitting locations in timed bursts meant that she only knew the
whereabouts of the animals periodically, but the life of the transmitter battery
packs were lengthened considerably. Even so, all of the spectacled eider transmitter
signals had faded completely away by December of 1994, well before their predicted
demise. It seems that the warm internal temperature of the eiders shortened the
battery life considerably.
Then in February 1995, a transmitter that had
gone silent the previous August suddenly sputtered back to life. Those involved
in the study will probably never know why this silent transmitter reactivated.
It could have been due to a loose power connection that finally wiggled back into
place or by the precise alignment of bird location, antenna angle, and satellite
position so that the weak transmitter signal was barely detected by the satellite.
Search Nears an End
Regardless, Larned and Balogh were soon in a small
twin-engine aircraft on their way to check out the location from which the signal
supposedly came. No birds were present at the coordinates downloaded from the
satellite. However, this method of obtaining precise locations of animals from
satellites becomes less precise as transmitter signal strength declines. Knowing
this, Larned and Balogh began their wandering search. It wasn't long before they
saw a brownish smudge on the stark white horizon. Thinking it was a spot of open
water, the first they had seen in some time, they flew towards it to check for
signs of life. As they approached, it became apparent that the smudge was actually
a few hundred spectacled eiders in a small ice hole. From there, another smudge
appeared in the distance, then another. They returned the next day to fly a systematic
grid search of the area. The eiders cooperated nicely. The biologists' flight
tracking software allowed them to record the precise coordinates of each flock
and prevent any flock from entering into the count more than once. Several hours
of flying and 25 eider flocks later, the aircraft fuel gauges indicated it was
time for them to start looking for an airstrip, rather pressing business in the
middle of the Bering Sea in the middle of winter. The largest flock they had seen
contained well over 30,000 eiders.
Although the biologists feel that most
of the flocks were found in their grid search of the area, budget and aircraft
fuel limitations made it impossible for an exhaustive search to be conducted.
Follow-up surveys in 1996 may shed more light on the winter distribution of this
bird. Hopefully, future research will reveal the winter diet of this species,
as it floats atop one of the most productive regions of ocean on the planet.
Last Updated: September 15, 2008