Citizen Science: Part of an ongoing series about everyday people adding to our knowledge of the world around us.

Today marks the beginning of what could be one of the largest citizen science projects in the country (or actually on the entire continent, now that Canada is involved): the Great Backyard Bird Count.

The idea is pretty much exactly what it sounds like: go outside, count the birds in your backyard (or wherever you happen to be at the time), and report the results to the Audubon Society and Cornell Lab of Ornithology. You can also submit photos to the project's Web site, see bird tallies from around the country, and compare data from previous years.

The results of this survey will be used to give scientists a snapshot of bird populations across the United States and Canada before spring migration begins, helping them evaluate everything from migration patterns to disease vectors to the impact of recent snowfalls (a.k.a. "snowmaggedon") that have blanketed parts of the country.

"Bird populations are dynamic; they are constantly in flux," according to the GGBC organizers. "No single scientist or team of scientists could hope to document the complex distribution and movements of so many species in such a short time."

That's why volunteers are needed, whether they're experienced birders or amateurs who just like the idea of being part of a gigantic science project. In 2009, volunteers across North America submitted 93,629 checklists for the bird count, reporting 11,550,200 individual birds of 619 species. New species were spotted, changes in range and habitat were documented, and several exotic birds were seen in places usually out of their range.

This is the 13th year of the Great Backyard Bird Count. Accumulating data over a significant period of the time makes the project more useful, especially when combined with other projects such as the Christmas Bird Count, Project FeederWatch, and eBird.

Last year, Audubon was able to use the data from 40 years of collective bird-watching to create a landmark State of the Birds Report. Their analysis showed that bird populations in the United States are declining at an alarming rate due to climate change, habitat destruction, invasive species, and other environmental forces. Nearly a third of the 800 species of birds in the United States are endangered, threatened, or in decline, according to the report, which U.S. Interior Secretary Ken Salazar called the disturbing news a "clarion call" for action.

Among the report's highlights, as reported by Scientific American:

• U.S. grassland bird species have declined 40 percent.
• Birds in arid lands have declined 30 percent.
• 39 percent of U.S. birds restricted to ocean habitats are declining.
• Some coastal shorebirds are doing well, but many face habitat losses and dwindling food supplies.
• Birds in Hawaii face a conservation crisis, with many species on the edge of extinction.

The year, data from citizen scientists contributed to another Audubon report showing the impact of climate change on bird populations. Nearly 60 percent of the 305 species found in North America during the winter are on the move, shifting their ranges northward by an average of 35 miles, according to the report.

By joining the bird count and contributing data from your own backyard, you can help scientists continue to study birds and their habitat. Find out how to participate in this year's count and download the data form and a bird checklist for your state or province at the project's official site.

Connect With Us: We'd love to hear about your birdwatching experiences this year or in times past. You can share them in the comments section below, become a part of NRDC's new We Love Birds social network, or sign up for your own blog here at OnEarth and join our community. You can also submit your birding photos to OnEarth's ongoing "Show Us Your Nature" contest. Your picture might even be selected to appear in the next issue of our magazine.

Read more stories in the Citizen Science series.