Backpack transmitters and GPS implants
Researchers have equipped 20 black oystercatchers with small backpack VHF radios, and another 14 with surgically implanted transmitters that broadcast the birds' movements as they migrate.
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Where do black oystercatchers go in the winter? How do they get there? Why do some migrate? Why do some migrate farther than others? These are a few of the questions biologists hope to answer by tracking oystercatchers this winter.
"This is the first time this has been done on this species," said Forest Service biologist Mike Goldstein of Juneau, referring to the implanted transmitters. The finger-size cylinders were implanted by veterinarians, assisted by biologists and volunteers. The data are transmitted via satellite and then e-mailed to researchers, who are making it available to the public via the Internet.
The route of the birds equipped with transmitters can be traced with Google Earth by going to the following Web site:
http://fresc.usgs.gov/products/blackoystercatcher/ptt_results.html.
Seven oystercatchers were tagged near Juneau in August. In early September, these birds moved 10 to 20 km north of their nesting territories near Portland Island.
"We're finding that there are some staging areas," Goldstein said. "The birds come out of nesting areas, congregate, then stage and maybe migrate together. We found something like 50 birds staging at Portland Island."
In mid-September, two males and a female moved 130 km south to the southern coast of Admiralty Island, and a female moved 500 km south near Dundas Island, B.C. As of mid-October, three birds had not left the Juneau area, and may overwinter.
"We think certain populations don't migrate, but the majority do migrate," Goldstein said.