Lynne Marsho, Peoria, IL

A birder in Illinois spotted this Bald Eagle during last year's Great Backyard Bird Count.

Warmer temperatures and lack of snow in parts of North America are setting the stage for what could be a most intriguing 15th annual Great Backyard Bird Count (GBBC), coming up Feb. 17-20.

Bird watchers across the United States and Canada are getting ready to tally millions of birds in the annual count coordinated by the Cornell Lab of Ornithology, Audubon and Canadian partner Bird Studies Canada.

In past counts, participants were most likely to report American robins in areas without snow. Will more robins be seen farther north this year? Will some birds, such as Eastern Phoebes, begin their migrations earlier? And where will the "Harry Potter" owl turn up next? Snowy owls have dazzled spectators as these Arctic birds have ventured south in unusual numbers this winter -- an unpredictable occurrence that experts believe is related more to the availability of food than to weather.

"This count is so much fun because anyone can take part -- we all learn and watch birds together -- whether you are an expert, novice or feeder watcher," said Gary Langham, Audubon's chief scientist. "I like to invite new birders to join me and share the experience. Get involved, invite your friends and see how your favorite spot stacks up."

Participants count birds at any location they wish for at least 15 minutes on one or more days of the count, then enter their tallies at http://www.birdcount.org. Anyone can participate in the free event, and no registration is required.

Last year, participants submitted more than 92,000 checklists with more than 11 million bird observations. These data capture a picture of how bird populations are changing across the continent year after year -- a feat that would be impossible without the help of tens of thousands of participants.

"This is a very detailed snapshot of continental bird distribution," said John Fitzpatrick, director of the Cornell Lab of Ornithology. "Imagine scientists 250 years from now being able to compare these data with their own. Already, with more than a decade of data in hand, the GBBC has documented changes in late-winter bird distributions."

To learn more about how to join the count, get bird ID tips, downloadable instructions, a how-to video, past results and more, visit http://www.birdcount.org. The count also includes a photo contest and a prize drawing for participants who enter at least one bird checklist online.

The Great Backyard Bird Count is made possible in part by sponsor Wild Birds Unlimited.