SUPERFLIGHT - winter migration of finches

National Wildlife, Dec-Jan, 1998 by Cynthia Berger

That's what scientists call the periodic movement of millions of finches from the North during the cold months

On a sunny april day in Upstate New York, a TV news van whipped into a shopping center parking lot. At the tables of a sidewalk cafe, people elbowed each other and pointed. Some celebrities were paying an unexpected visit.

Were they foreign heads of state? Nobel prize-winning physicists? Rock stars? Reasonable guesses in Ithaca, New York, the home of Cornell University -- but wrong. No, the visitors were birds -- small, reddish, sparrowlike birds with odd bills that crisscrossed at the tip.

The little flock of red crossbills and white-winged crossbills had alighted in a tall Norway spruce at the edge of the parking lot. A rare sight in New York, they were the retreating wave of a spectacular winter- long and continentwide invasion -- a so-called Superflight.

Crossbills are members of a bird group that scientists call "winter finches" because they sometimes show up in unusual places in the winter. The winter finch roster also includes the pine siskin, purple finch, evening grosbeak, pine grosbeak, common redpoll and hoary redpoll -- all members of the finch family. (Only three species of North American finches are not winter wanderers: the lesser goldfinch, Lawrence's goldfinch and house finch.) Red-breasted nuthatches, which are more closely related to chickadees, might also be considered honorary "winter finches" because of their similar feeding -- and wandering -- habits.

Winter finches normally live year-round in the boreal forests of Canada and Alaska, or high in the Sierra Nevada, Cascades and Rocky Mountains. These are birds whose lives are inextricably bound with vast dark forests of evergreen trees. They feed on tree seeds: Crossbills eat the brown seeds of conifer cones; redpolls eat the small seeds within the caterpillarlike catkins of birch and alder trees; pine grosbeaks eat buds and the seeds of ashes, along with berries from many shrubs. Winter finches are hardy birds, adapted to extreme cold and deep snow.

But some winters the finches, like rock stars, go on tour. It's not that ice and snow are a problem, it's that birds, like balladeers, have to eat. Last winter they hit the road by the millions (scientists don't know exactly how many), making headlines across the country. White-winged crossbills were spotted in Tennessee, common redpolls visited Virginia, evening grosbeaks paid a call in South Carolina and red-breasted nuthatches dropped in to Texas.

When a single species wanders out of its usual home range, the phenomenon is called an "irruption." When many kinds of winter finches irrupt simultaneously, that is a "Superflight," a term coined by ornithologist Carl Bock of the University of Colorado at Boulder. Bock had noticed general patterns to irruptions: Redpolls seemed to invade every other year, for example, and evening grosbeaks every three or four years. Beginning in the late 1960s, Bock and his students examined data from the National Audubon Society's Christmas Bird Count (a yearly volunteer-based bird survey) to see if irruptions of different species were synchronized. Did winter flights of crossbills and redpolls happen at the same time? Did the birds invade the eastern and western United States simultaneously?

"The Christmas count data supported these ideas," says Bock. "Irruptions did seem to be widely synchronized. What was especially striking was that there seemed to be certain years -- kind of unpredictably -- where the synchrony was stronger, where the birds came in bigger numbers and went farther south, and everyone was seeing them everywhere." During these Superflight years -- 1968-69, 1972-73 and 1982-83 -- anything was possible. Bock remembers the year red-breasted nuthatches were spotted perching on fence posts in a cemetery on the plains of eastern Colorado -- hundreds of miles from the nearest tree.

The 1997-98 Superflight was documented with the help of the Internet. Steve Kelling, an avid bird-watcher and employee at the Cornell Laboratory of Ornithology, logged onto a local birder's listserv one October day and saw that several different kinds of winter finches had been sighted around Ithaca. That prompted Kelling to put in a query to a national listserv: "Anyone else seeing winter finches?"

"I got a tremendous response," he says. "Finches were everywhere -- Maine, Texas, Oregon, Washington. I collected the information, put dots on a map, and realized it was going to be a Superflight."

Bird-watchers were asked to report their winter finch sightings online, using a special winter finch survey form on BirdSource, a new web site developed by Cornell and the National Audubon Society. By May, more than 8,000 online finch surveys had been filled out and submitted electronically. "Nobody really knew the dynamics of a winter finch irruption: how quickly do they travel, do they go to just one area or many places, do they stop when they find food, or do they keep wandering all winter?" says Kelling, the BirdSource project leader. Researchers are still wading through the data to find answers to most of these questions. But the weekly reports allowed Kelling to produce animated maps, viewable on the BirdSource web site, that show just how the birds moved about.