This week-end, Friday through Monday, marks the annual Great Backyard Bird Count, sponsored by the Cornell Lab of Ornithology and the National Audubon Society. You can contribute by watching birds in your backyard for as little as 15 minutes during one day of the count.
Last year, birdwatchers in Canada and the United States submitted more than 97,200 checklists and saw more than 602 different species of birds. The collected data is used by scientists to track migration patterns and spot trends in bird populations. In 2010, the American Robin was the bird most commonly sighted; the Red-billed Tropicbird made it onto the list for the first time.
Here's everything you need to know about how to participate. The Cornell Lab of Ornithology has an online bird guide with descriptions of 585 birds - including pictures and bird calls. If you are new to birding, you might want to start with the 51 most common bird species sighted in North America. You can also search for a birding walk or workshop in your area.