Friday, December 6, 2013
(Continued from page 1)
Biologist Patrick Keenan helps Morgan Earls, a Waynflete student, release a veery after banding it Tuesday at River Point in West Falmouth.
Photos by John Ewing/Staff Photographer
Biologist Kevin Regan holds a Nashville warbler that had been netted and was being banded before its release.
"At River Point, we're interested in timing, abundance and diversity of migratory songbirds," said Keenan, who has banded for three years in the 41-acre sanctuary at River Point.
Data from other species, including game birds, are analyzed in many locations across the U.S. and are essential in detecting changes, especially in sizes of populations, according to the Bird Banding Laboratory in Laurel, Md. The data are used to evaluate hunting pressure on species, estimate productivity and survival and determine how vulnerable different ages and sexes are to hunting or other predation.
In comparison, bird-watching, which also yields significant information, is limited to some degree -- by the numbers of birders and their subjective perceptions.
But one Maine program, led by Colby College professor of biology Herb Wilson, is comprehensive, with 18 years of data on migratory patterns of songbirds. Assisted by more than 200 volunteers, Wilson has compiled enough data to conclude that the climate is warming. "And," he said, "the pace at which this is happening is unparalled in history on Earth.
"The birds are giving us a signal -- there's going to be accelerated warming," Wilson said. Manifesting the fallout consequences of global warming, birds are sentinels, he said. "They're a literal canary in the coal mine."
Some bird-banding experts, however, are more reticent to draw specific correlations.
Robby Lambert, assistant wildlife biologist at BRI, has been involved in bird banding for more than a quarter-century, working all over the nation. He is very cautious about speculating about what birds may be revealing. He's certain, for example, that Southern species are moving northward -- but not so sure why.
"Things are changing," he said. "To deny that something is happening in the environment would be foolish." But, deeper understanding takes time. "It's a very, very long process," he said.
"You build up a pretty good database (with) .... the unbiased monitoring of the net," Keenan said. "And it is highly cost-effective," requiring only nets, bands (provided by the U.S. Geological Survey), small scales to weigh the birds and the time and labor of a small staff of biologists.
Banding with mist nets allows for intensive study of individual birds that return, year after year, to almost the exact spots.
For example, gray catbird 241150588 swooped into Net 7 at River Point on 5/31/11 and again in the same net on 6/20/12, giving ample evidence that the species returns to the same nesting area year after year.
In such minutiae may lie clues to a range of scientific queries. They may also ensure that these particular biologists are likely to migrate back, too.
"It's a labor of love," Lambert said. "I like to handle the birds. I look for (trends). I appreciate that. It gives you a sense of what's going on."
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Patrick Keenan holds a Canada warbler for students. “At River Point, we’re interested in timing, abundance and diversity of migratory songbirds,” he said.
John Ewing/Staff Photographer