If you enjoy feeding and watching backyard birds, the Great Backyard Bird Count (GBBC) is a great way to spend a weekend. Sponsored by the Cornell Laboratory of Ornithology and the National Audubon Society, the 11th annual event, Feb. 14-17, is a continent-wide research project.

It's a great way to dabble in citizen science.

Begun in 1998, the GBBC enlists birders of all skill levels in this effort to keep common birds common. Even if you can identify only cardinals and blue jays, you can make a valuable contribution. Last year these "citizen scientists" turned in a record 81,203 checklists reporting a total of 613 species consisting of 11,082,387 individual birds.

"The GBBC is a great way to engage friends, family and children in observing nature in their own backyard, where they will discover that the outdoors is full of color, behavior, flight, sounds, and mystery," says Janis Dickinson, director of citizen science at the Cornell lab.

What began as an exercise in backyard birdwatching 11 years ago has morphed into true science.

"There has never been a more detailed snapshot of continental bird-distribution profile in history," says John Fitzpatrick, director of the Cornell Lab of Ornithology. "Imagine scientists 250 years from now being able to compare these data with their own."

The GBBC can help answer basic questions such as: How does winter's snow and cold temperatures influence bird populations? Where are the winter finches and other irruptive species? Is global climate change affecting winter bird populations?

To participate in the GBBC, log on to the GBBC Web site and follow the instructions. To ensure birds are not counted more than once, counters simply tally the highest number of each bird species seen at one time and keep track of the time spent counting. The time invested can be as little as 15 minutes. To simplify the process, you can click on your state for a checklist of the most frequently reported birds in your area. There is no fee required.

Results are updated hourly in the form of animated maps and colorful graphs for all to view. This near-instant feedback allows participants to see almost immediately how their observations fit into the continental perspective. Results from previous years' GBBCs are also available online.

Because the GBBC reports its results in real time, scientists can quickly detect interesting relationships between weather and bird movements. For example, in some winters robins have been reported farther north than usual. Turns out snow cover was the key. Where snow cover was scant, robins occurred farther north than expected. Perhaps heavy snow makes food difficult to find and drives robins south.

The GBBC also helps track the movements of northern finches. Evening grosbeaks, common redpolls and pine siskins, for example, move southward in great numbers some winters. Lab director Fitzpatrick attributes this to a lack of food on what are typically the birds' northernmost year-round ranges.

Participants can invest as little or as much time as they choose. Tonya Daft of Mannington, W.Va., for example, will be counting for the first time this year, but she has recruited 23 helpers from the youth-oriented Buffalo Creek Dream Makers Conservation Club. She is also encouraging participation by students at the Barrickville Elementary and Middle School.

"I think it's important that kids get involved with conservation projects at an early age," she says.

Janet Bronder of Pittsburgh would no doubt agree. She started feeding birds when her children, now 24 and 17, were young. In November, she opened a backyard bird store, the Songbird Sanctuary in Blawnox, and she's already recruiting customers to participate in this year's GBBC.

"It's a great way for an entire family to spend the weekend," she said.

Elizabeth Alakszay of West Chester, Pa. has been counting for the GBBC since its second year.

"I do it because it's a great way to express my concern for the environment and wild bird populations," she explains. "I'll spend about 16 hours over the entire weekend and visit a variety of habitats beyond my backyard."

Pat Leonard, a spokesperson for the Cornell lab, measures GBBC success in a variety of ways.

"We are seeing an increase in the number of local events based on the GBBC, particularly by youth and school groups," Leonard said. "And last year, we received more than 4,000 photographs from participants, many of surprising quality. So this year, we're asking counters to videotape their best birds and post them on YouTube."

In addition to results, the GBBC Web site includes a variety of other useful birding information including vocabulary, photos, vocalizations and birdwatching and bird-feeding tips. It's a valuable resource for all birders, especially students.

GBBC backers say the event presents an opportunity for individuals, families, schools and community groups to contribute to a better understanding of wild birds.

For more information about the GBBC or the Cornell Laboratory of Ornithology, contact the lab at 159 Sapsucker Woods Road, Ithaca, NY 14850, www.birdcount.org, or call 800-843-2473.