Colorado’s two biggest cities are continuing a birding tradition this holiday season — one more than 100 years old across the nation.

Dating to 1900, the National Audubon Society calls the Christmas Bird Count the country’s longest-going community science project dedicated to our winged neighbors. Since one of the organization’s early officers, Frank M. Chapman, got enthusiasts to spend Christmas Day tallying what they saw in neighborhoods from California to Canada, many more communities have joined the cause from mid-December through the start of the new year.

That includes Colorado Springs, where the count is set for Dec. 17, followed by Denver on Jan. 1. Locals can add to the historic catalog that researchers and wildlife officials have used to study the long-term health and status of the continent’s birds. The data were used, for example, to inform Audubon’s 2014 report on climate change, which raised the alarm on ranges being altered for most of North America’s species.

The Springs’ Aiken Audubon reminds: “You don’t have to be a bird expert and can contribute right from your backyard.” The canvass circle, mapped online, includes 20 areas covering all parts of the city. To contribute, reach out to Tyler Stuart at [email protected].

On New Year’s Day, Denver Audubon has scheduled counts around City Park, Cherry Creek State Park, along the South Platte River and other neighborhoods. Sign up on the group’s website.