The United States and Canada just basked in an
unusually mild winter.
Temperatures ranked fourth warmest on record, according to the National
Oceanic and Atmospheric Administration, and
many spring flowers are
already blooming. But did the birds notice? Definitely, according to the
Great Backyard Bird Count (GBBC), an annual tally of bird sightings
collected by amateur birders across the United States and Canada. The
numbers reveal that the
snowy owl population in particular boomed and
that many other birds showed up in more northerly latitudes than usual.
 |
Spotted. Amateur birders counted more than four times as many snowy owls in the
United States and southern Canada as last year. |
GBBC, now in its 15th year, is a joint effort by the Cornell Laboratory
of Ornithology in Ithaca, New York, and the National Audubon Society,
headquartered in New York City. This year, birders, who were instructed
to identify and record whatever birds they happened to see in their
yards and neighborhoods between 17 and 20 February, tallied 17.4 million
individual sightings. Pat Leonard, GBBC's director of communications,
says that it's unclear how many individuals took part because each
observer can submit more than one sighting checklist, but he estimates
that between 65,000 and 70,000 volunteers participated.
Ornithologists working with GBBC analyzed the data and found a number of
unexpected trends. One of the biggest surprises, says Marshall Iliff,
an ornithologist at the Cornell lab who co-authored the report and leads
a smaller, year-long project similar to GBBC called eBird, was an
explosion in sightings of the snowy owl (Bubo scandiacus). In
November, reports began trickling in to eBird that the snowy owl, which
primarily lives north of the Arctic Circle, was showing up in
unexpectedly large numbers in the United States and southern Canada, and
GBBC's tally backs that up. Observers reported 428 sightings of the
owl, which is four times the number from the same time last year. "This
snowy owl thing is pretty surprising," Iliff says.
So what's driving the bird's southern influx? One possibility,
Iliff says, might be that the owl's primary prey source, lemmings, could
be sparser than normal in Arctic latitudes, which would lead more owls
to seek food farther south. But that's unlikely because lemming
populations have actually being doing quite well this year, writes
Robert Ostrowski in an e-mail. Ostrowski is an experienced birdwatcher, a
member of the Maryland Ornithological Society's records committee, and
isn't involved with GBBC. "One possible explanation," he says, "is that
the snowy owls had such an ample amount of food available that their
reproduction success was higher than normal, causing an over-population
of birds that were eventually forced south by competing individuals." - Science Now.
