Tens of thousands of bird watchers across the U.S. and Canada participate each winter to create a snapshot of the whereabouts of more than 600 species of birds and provide a basis to study bird population trends. This year’s count takes place from Feb. 17-20.

Organizers are encouraging participants to count birds in their backyards, in parks and other locations and report their observations online. The event is organized by the National Audubon Society, the Cornell Lab of Ornithology and Bird Studies Canada.

In last year’s event, Mainers identified 99 species with more than 42,000 bird observations.

More information is available at birdsource.org .