For over a century the Audubon Society has organized a massive citizen science undertaking: The Christmas Bird Count. Tens of thousands of volunteers help take a census of the bird populations of Canada, the United States, Mexico and Central and South America.
Data from the annual surveys has provided biologists and conservationists a picture of long term changes in the distribution of North American bird populations.
For example, analysis of data collected over the past 40 years shows that the the winter range of many bird populations - 177 of the 305 species examined - has shifted north, in some cases hundreds of miles. The shift correlates with an increase in mean January temperatures of almost 5 degrees during that period, and it's likely that climate change is at least partially responsible. Based on that data, the Audubon Society's report on birds and climate change (pdf) concludes that "ecological disruptions that threaten birds, other wildlife and human communities [due to climate change] are likely already in motion".
On the other hand, doves and pigeons have expanded their ranges along with growing urban and suburban development.
It's data that would be difficult to collect without an army of volunteers.
If you'd like to participate, this year's Christmas Bird Count begins on December 14th and runs through January 5th. You'll need to register for a count:
There is a specific methodology to the CBC, but everyone can participate. The count takes place within "Count Circles," which focus on specific geographical areas. Each circle is led by a Count Compiler. Therefore, if you are a beginning birder, you will be able to join a group that includes at least one experienced birdwatcher. In addition, if your home is within the boundaries of a Count Circle, then you can stay home and report the birds that visit your feeder once you have arranged to do so with the Count Compiler. There is a $5 fee to participate in the CBC for all field participants aged 19 or older.
Find a count circle near you (unfortunately only searchable by state or province).
Even if you can't participate in the Christmas Count, you might be interested in similar bird observation projects:
- The Great Backyard Bird Count (February 18-February 21)
- The Cornell Lab of Ornithology "Celebrate Urban Birds" Project
Images from from Our Winter Birds: How to Know and How to Attract Them by Frank M. Chapman (1918). Chapman, an ornithologist with the American museum of Natural History and officer in the Audubon Society, proposed the first Christmas Bird Count in 1900. Top image: Tree Sparrow. Bottom Image: Northern Shrike.