As Maine residents celebrate the arrival of spring, seabird biologists are eagerly awaiting the return of Arctic terns to a small number of islands along the coast of Maine. Some of these terns are wearing small tracking devices that will allow biologists to reconstruct the details of an incredible migratory journey that these birds have undertaken in recent years.
Seabird biologists have long wanted to study Arctic tern migration between islands along the coast of Maine and their wintering grounds in the Southern Hemisphere. In 2010, biologists from the US Fish and Wildlife Service’s Maine Coastal Islands National Wildlife Refuge and National Audubon Society’s Seabird Restoration Program deployed 30 geolocators on Arctic terns breeding on Metinic Island (Matinicus Isle) and Eastern Egg Rock (St. George).
Geolocators are small electronic devices that estimate the location of a bird based on the length of daylight and the time of sunrise and sunset. Prior to this tagging effort, managers could only guess where they traveled.
In May 2012 two tagged birds were found nesting on Matinicus Rock, where Audubon biologists were able to remove the geolocators which contained two years of migration data. This provided new insight into Arctic ternmigration, as the two individuals followed roughly similar paths in each of the two years. The data revealed some amazing migration patterns and use of three important marine bird areas, including an area mid-Atlantic between Nova Scotia and Spain, an area off of southern Argentina and a wintering area in the Weddell sea east of the Antarctic Penninsula All birds left the Gulf of Maine and flew towards northeastern Nova Scotia; however three distinct patterns were used during the remainder of the fall migration. After flying east across the Atlantic Ocean, three birds flew south along the west coast of Africa before flying into the Indian Ocean.
Four birds flew along the west coast of Africa and then flew to the east coast of South America. The remaining six birds flew south through the middle of Atlantic Ocean before spending time along the east coast of South America. During the fall migration the birds traveled an average of 27,168 miles (average of 296 miles/day). The average length of time to reach the wintering ground was 92 days.
The birds wintered along the Antarctic ice pack for an average of 152 days, where they logged an additional average of 14,100 miles. When it was time to return to the breeding colonies, the birds seemed in more of a hurry and all took the same general route back to Maine. The average spring migration was 13,988 miles (average of 472 miles/day). This project confirmed that Arctic terns have the longest known annual migration. Including their winter wanderings near Antarctica, they travel an average annual distance of 55,250 miles round trip. Arctic terns can live for over 30 years, so that during their lifetime they may fly an equivalent of 66 times around the Earth or three round trip flights to the Moon.
While US Fish and Wildlife Service and National Audubon Society seabird managers are doing all they can to protect the Maine Arctic tern colonies, Linda Welch, biologist for the Maine Coastal Islands NWR notes: What happens if the abundance and distribution of critical food resources are changing because of climate change? Will the birds be able to find enough food to fuel their bodies during migration? Stephen Kress, Director of Audubon’s Seabird Restoration Program concludes: “ the study points to the importance of protecting the terns entire world range, including the sensitive feeding areas at sea. The study demonstrates that the Arctic Tern belongs to both hemispheres and individual birds require secure passage through four continents. Their flyway is the full Atlantic Ocean”.
There are already signs that something might be adversely affecting Arctic terns. The entire Gulf of Maine population has declined over 40% in the past 10 years to about 2,500 nesting pairs. Previously, Machias Seal Island, located on the U.S. Canadian border was historically the largest Artic tern colony in the Gulf of Maine, supporting over 2,500 pairs of Artic terns. However, that tern colony has not produced any chicks since 2006 and few terns even attempt to nest on the island. In Maine, Arctic terns are listed as a threatened species and in 2012, Arctic terns only bred on four islands.
The geolocators deployed in 2010 will continue recording data for several years and can store data for 8-10 years. See Downloadable Resources section below for a map of the migratory journeys.
Watch the Arctic Tern live cam and other seabird cams by clicking HERE.
Contact: Linda Welch, Wildlife Biologist, 207-546-2124x11, Linda_Welch@fws.gov
Contact: Dr. Stephen Kress, Director Audubon Seabird Restoration Program, 207-529-5828, firstname.lastname@example.org
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