CONCORD - A Canada goose from Greenland that was spotted in Concord last month signals a change in migration patterns that could be another sign of global warming, authorities say.
Local resident David Swain had spotted the big goose in a gaggle of "300 of his close friends" at Nine Acre Corner in Concord.
Swain could easily read "GJL" in black letters on a large yellow band through his spotting scope. He was curious about the bird's origins, and reported the sighting to the Patuxent Bird Banding Laboratory in Maryland on Dec. 15.
Not long after that, a researcher from Denmark contacted Swain and identified the goose as one of 42 that were banded in 2008 for ongoing research in Greenland into the decline of a rare white fronted goose.
"It was very cool, " said Swain, who is an associate professor of English at Southern New Hampshire University.
Geese that were banded in Greenland have also been sighted at the University of Massachusetts Amherst, in South Egremont and in Sheffield.
That a goose flew almost 2,000 miles, much of it while crossing the Gulf of Labrador, is nothing new. But that Canada geese, whose species is relatively new to Greenland, appear to have widened their territory to Massachusetts tells a different story, perhaps one of global warming, said H.W. Heusmann, a wildlife biologist at the Massachusetts Division of Fisheries and Wildlife.
With a gradual warming of the climate, Heusmann said, geese are not wintering as far south.
"Wildlife is ahead of the curve when it comes to global warming,’’ he said.
Wayne R. Petersen, director of the Massachusetts Important Bird Areas Program for the Massachusetts Audubon Society, said that in the past birds from Greenland did not migrate to North America. They migrated exclusively to Europe. The Concord goose represents a new migration route.
“A change in migration pathways may be an indication of climate change,” Petersen said. “The Concord goose gives us a heads-up on the comings and goings of other rare birds.”
Petersen said other birds that are increasingly spotted in Massachusetts include the barnacle goose and the pink-footed goose, both of which breed in Greenland, Iceland and Sweden. These geese are possibly also modifying their migration, Petersen said. Rare birds that have recently been spotted in Massachusetts might not be so unusual in coming years.
Canada geese first showed up in Greenland in the 1980s and are believed to be a contributor to the decline of the rare Greenland white-fronted goose. The number of white-fronted geese has dipped dramatically, while the number of Canada geese has exploded in Greenland, as it did in Massachusetts.
David A. Stroud, an ornithologist with the United Kingdom Joint Nature Conservation Committee, said in an e-mail that shifting weather patterns bringing more snow in April, and the growth of the Canada goose population in Greenland have hurt the white-fronted goose.
"Not only are their essential feeding areas covered in deep snow when they arrive, but if they can find feeding they now have to compete with the larger bodied, more aggressive Canada geese that are now sharing the landscape," said Stroud.
Prior to the 1980s, Canada geese were not a factor in Greenland, said Petersen.
“They did not colonize there for one reason. Conditions were just not suitable,” he said. “The Concord goose, this is a bird we know is coming and going to Greenland. The Canada goose never did that. The climate may be just warm enough to just possibly allow it."
Of course, while a Canada goose from Greenland may be unusual, the bird is quite well known to Massachusetts residents.
The year-round population of Canada geese in the state is estimated at 40,000. Heusmann said there could be as many as 800 geese grazing in Concord pastures at one time. The Greenland goose likely hit Massachusetts in a "truck stop approach," after seeing resident geese.
The resident population descended from geese that were imported to Massachusetts from the Midwest and bred in captivity to be used as decoys for hunting a century ago. When the practice was outlawed in 1935, many hunt clubs released their flocks into the wild. By then, the birds had lost their migratory instinct and never left the state, said Petersen.
By the mid-1960s, the geese had spread across the state and reached nuisance levels.
Heusmann said the majority of migratory geese, estimated at a worldwide population of 400,000, pass over Massachusetts, but some take up winter residence here. While geese bond with their mates, Heusmann said, there is no evidence that migratory geese mate with residents.
"There's no evidence of the ganders pairing," he said. "There's no data that supports pair bonds. There's no single case of a goose banded in Quebec nesting down here."
Resident geese are prolific and reproduce year after year. Heusmann said a pair were sighted on a pond at Fort Devens and within seven years their offspring had grown into a flock of 180 birds.
"There's too many geese everyplace, they're so successful and so prolific," said Heusmann.
"There are no biological problems with these birds. They are not a problem to the natural environment. They are a problem to the human environment," he said.
While the Canada goose is not a threat to native species, Heusmann said, it's the man-created stuff, like lawns, that are threatened.
"If geese didn't defecate, they wouldn't be considered nearly the problem that they are," said Heusmann.