|Argos Newsletter N° 51 - August 1996|
Margaret R. Petersen
Alaska Science Center
Spectacled eider tracking
One of the last big mysteries of North American waterfowl has been the location of molting and winter-ing areas of the Spectacled Eider (Somateria fischeri). It is even more mysterious since Spectacled Eiders spend nine to eleven months (females and males, respectively) at-sea, and flocks of birds have not been reported.
In the 1970s a U.S. Fish and Wildlife Service (FWS) biologist studying the birds in Alaska (Christian P. Dau, Bethel, Alaska) suggested that a study be initiated using satellite telemetry to learn their at-sea distribution. However, funding was not available nor were transmitters small enough (30 to 40 g) to place on birds weighing from 1000 to 1500 g. Conventional telemetry to find areas where birds concentrate in winter somewhere in the Bering Sea was impractical because of the great expense and the high personal risk of flying small airplanes there. In winter the amount of daylight is markedly reduced at 58 to 65°N latitude, winter storms are frequent and often unpredictable, and fog often blan-kets the area.
When it was shown that between the 1970s and 1990s nesting populations had dropped by 96% on the major nesting area in western Alaska, the species was listed as threatened under the Endangered Species Act. It was possible that some change in habitat or some perturbation at-sea could have contributed to the decline, especially considering they spend most of their life at sea. Without the basic dis-tribution information no assessment was possible. As a result I initiated a study using satellite Platform Transmitter Terminals (PTTs) as an aid to determining the at-sea distribution of Spectacled Eiders.
By the early 1990s small PTTs were in use by biologists studying birds in many locations throughout the world. Those transmitters were large (>45 g) and attached by back-pack harnesses, glued to the feathers, or attached to neck col-lars. These techniques were inappropri-ate for diving ducks because of delete-rious changes in their behavior with those attachment techniques. Because of this behavioral response, we decided to imp-lant the transmitters. This technique was being developed by C. E. Korschgen (U.S. National Biological Service, La Crosse, Wisconsin, USA) and success-fully used on diving ducks. By 1993 a PTT transmitter weighing 30 g, which could be hermetically sealed and was small enough to fit in the body cavity of an eider, had just been developed and tested by Paul W. Howey (Telemetry 2000, USA).
In 1993 we deployed 12 PTT transmitters in western Alaska, in 1994 22 PTT transmitters in western Alaska, and in 1995 30 PTT transmitters in Russia (10) and western and northern Alaska (10 each at 2 locations). Deploy-ment involved placing the transmitter in the peritoneal cavity of the bird with the percutaneous antenna exiting caudally. The transmitter was 10 mm deep, 55 mm long, and 35 mm wide. Each was encased in a hermetically sealed package with a teflon-coated multistrand stainless-steel antenna. Transmitters were programmed and calibrated to provide body temperature and remaining battery potential with each transmission.
Results from the first year were sufficient to satisfy the skeptics who did not believe it could be done. From the loca-tion information, I could delineate at-sea areas for Bill Larned (FWS, Soldotna, Alaska) to concentrate his aerial survey efforts. From the location data and the survey data, we quickly identified and documented a previously unknown post-nesting molting area of female Spectacled Eiders from western Alaska. I also provided at-sea locations for males which, after they leave the breeding grounds, congregate on molting areas at-sea. One area could not quickly and easily be surveyed since it was in Russian waters, and only a few hundred birds were found at the other location. Plans were made to continue the study with an improved version of the transmitter in 1994, and early in the year FWS personnel begin the necessary diplomatic work for an American pilot/biologist (John Hodges, FWS) to fly an American government owned aircraft (a turbo Beaver) in Russian airspace.
During the next two seasons, from the PTT locations and the data gathered
from aerial surveys in Russia and Alaska, we delineated:
The 1994 aerial survey in waters off eastern Russia was very successful. The FWS biologists received good co-operation from the Russian officials and found a large (>10,000) concentration of birds. They attempted to duplicate the effort in 1995 with the hope to expand into the areas off northern Russia where we suspected many males molted. The political climate and spirit of cooperation at some regional and local levels had changed by 1995, however, and only part of eastern Russia was surveyed.
From the surveys conducted at-sea, it became clear why few observations of molting or staging Spectacled Eiders had been recorded. These birds congregate in very dense flocks far from land, they frequent areas few vessels visit in summer and fall (and none in winter), and they are easily missed if the survey plane is not within a few km of a flock. The birds are far from land and beyond the distance usually flown by single engine aircraft. Although by fall 1994 we knew much more than before about the at-sea distribution of eiders, we still did not know where birds were in midwinter (January-March). It was not until February 1995 when a single location was received from a bird from what seemed the middle of the pack ice in the Bering Sea. Based on that location, Bill Larned flew to that general area and located dense flocks of Spectacled Eiders in holes in the pack ice north-east of St. Matthew Island, Alaska. Bill flew again in March, and he photographed tens of thousands of eiders. At long last, we believe we have found the primary wintering area of Spectacled Eiders.
As of late winter 1996, surveys have been delayed for four weeks because of weather and mechanical problems. The plan is to survey the wintering area located in 1995 and adjacent areas. I expect to deploy transmitters on 12 males and 12 females from the northern Alaska breeding area in summer 1996.
By the time the project is finished, we hope to: