Bird and nature fans throughout North America are invited to join tens of thousands of everyday bird watchers for the 12th annual Great Backyard Bird Count Feb. 13-16.

The count, a joint project between the Cornell Lab of Ornithology and National Audubon Society, invites individuals, families, schools and organizations to count birds. Participants count birds at bird feeders, and in backyards, local parks and other locations.

Those tallies are then reported online through the BirdSource Web site at http://www.birdsource.org/gbbc.

The data these “citizen scientists” collect helps researchers understand bird population trends, information that is critical for effective conservation. Their efforts enable everyone to see what would otherwise be impossible: a comprehensive picture of where birds are in late winter and how their numbers and distribution compare with previous years.

More than 85,700 checklists (an all-time record) were submitted in 2008, recording the activity of 635 bird species. In Maine, 767 checklists were submitted last year, listing 96 species.

“We are hoping for even more checklists from Maine for 2009, to track our extraordinary bird activity, including a number of irruptive birds (birds that migrate based on natural food source availability), species like the red-bellied woodpecker, cedar waxwings and robins, which have been seen in large flocks all over the state,” said Laura Turner, owner of the South Portland Wild Birds Unlimited Nature Shop.

Anyone may take part, from novice bird watchers to experts, by counting birds for as little as 15 minutes (or as long as they wish) on one or more days of the event and reporting their sightings online at www.birdcount.org.