As winter finches move south across the Canada-U.S. border in what may be record numbers, ornithological scientists are getting their best-ever look at a massive bird 'irruption,' thanks to thousands of citizen scientists with one hand on the binoculars and the other on the computer keyboard.

The scientists are monitoring BirdSource http://birds.cornell.edu/pfw, the interactive World Wide Web database for bird information that is operated by the Cornell Laboratory of Ornithology and the National Audubon Society. The online database records bird sightings -- by casual backyard bird-watchers as well as serious bird enthusiasts -- and reveals where the birds are anywhere in North America.

For reasons that scientists soon hope to explain, winter finches that normally stay in Canada are invading the United States this season, and BirdSource opened to the public just in time to record that irruption. Online birders in the United States are reporting unprecedented numbers of winter finches, which include the pine siskin, red crossbill, white-winged crossbill, pine grosbeak, evening grosbeak, purple finch and hoary redpoll.

"We need to know which birds are where, and the best way to get this information is to ask bird-watchers across the continent to share their sightings," said Frank Gill, senior vice president for science at National Audubon.

"These irregular migratory movements may be associated with a particularly successful breeding season, followed by a shortage of essential winter food seeds," said John Fitzpartick, director of the Cornell Laboratory of Ornithology (CLO). "Never before have we been able to track winter bird movements on this large and dynamic a scale. Still, more information is needed to fully understand this phenomenon, and bird-watchers, by contributing their sightings through BirdSource, are playing an important role in deciphering the mysteries surrounding irruptions."

Two citizen-science projects, Project FeederWatch and the new North American Winter Finch Survey, have been essential in gathering the winter finch information. FeederWatch participants count the birds that visit their feeders over the winter according to an easy-to-follow

protocol. Since 1987, FeederWatch has grown to include more than 11,000 participants annually. In November, the project came online as part of BirdSource, and the implications of this Web accessibility already are being felt. Diane Tessaglia, research coordinator for Project FeederWatch, has been able to determine that already, 16 percent of online FeederWatchers are reporting pine siskins, 15 percent are seeing purple finches and 10 percent are tallying evening grosbeaks.

"Last year, evening grosbeaks just weren't seen at feeders in the eastern U.S.," Tessaglia recalled. "But this year, they've already been reported as far south as New Jersey. Something interesting is happening," she said, noting that many other finches, like the common redpoll that typically stays in Canada year-around, are seen as far south as Virginia.

Information from the study, which is housed at a database at the Cornell Theory Center, is updated as reports come in over the Internet. According to Rick Bonney, director of education at CLO, Project FeederWatch alerts users when "errors" are suspected -- for example, when an

unlikely bird species in a particular geographic region is reported.

"The user can correct the mistakes before the data are entered. Therefore, the information in the BirdSource database is not only instantly accessible, it also is remarkably free of errors," Bonney said. "And if the user really meant to report an 'unlikely' species, we are automatically alerted to a possible rare bird sighting anywhere in North America."

The other key element in BirdSource is the North American Winter Finch Survey. CLO scientists quickly launched the survey when winter finches were posted to bird listservs (e-mail mailing lists) in more southerly locales in surprising numbers.

"When common redpolls were reported in Maryland by mid-October, we developed a way to track what we suspected would be a monumental season for winter finches," says CLO web master Steve Kelling, who engineered the survey. "The invasion has been even more phenomenal than we expected."

The North American Winter Finch Survey asks bird-watchers to note the numbers of individuals, the date and postal ZIP code where their winter finch sightings occurred. Animated maps are regularly updated to show how each species is moving south. With a click of a mouse button, anyone can see an image of these rare northern wanderers -- each a dazzling combination of either pinks and browns or yellows and browns -- and users can hear their chattery trills, rattles and warbles.

National Audubon's Frank Gill points out that the winter finch information received so far is only a fraction of whats out there. "If everyone who feeds and watches birds would contribute their sightings, the database would be tremendous," he said, inviting anyone interested in birds to be join a "history-making event" by signing up for Project FeederWatch.

FeederWatch participants receive a research kit, which includes easy-to-follow instructions, tips on how to attract birds and a colorful, illustrated poster of some of the birds that are likely to visit their feeders. FeederWatchers also receive the quarterly newsletter Birdscope, which highlights recent findings such as the winter finch invasion. A $15 annual fee helps to cover the cost of materials.

FeederWatchers can get a password and can contribute their data online through BirdSource. For more information or to sign up, call toll-free 1-800-843-2473 (BIRD). In Canada, call 519-586-3531. Or write Project FeederWatch/BSO, Cornell Lab of Ornithology, 159 Sapsucker Woods Road, Ithaca, NY 14850.

Any sightings of winter finches can be contributed directly to the North American Winter Finch Survey without joining or paying a fee. Both the Winter Finch Survey and Project FeederWatch can be accessed through BirdSource at http://birds.cornell.edu/pfw.

"BirdSource is the perfect marriage of Cornell's high-tech computer capabilities, the Cornell Lab of Ornithology's citizen-science team and Audubon's thousands of volunteer birders collecting data at the grassroots level," said National Audubon Society President John Flicker.

BirdSource scientists currently are working to expand the technology to include all of CLO's citizen-science projects as well as Audubon programs such as the annual Christmas Bird Count.