The Audubon Society’s 123rd Christmas Bird Count (CBC) will take place Dec. 14 through Jan. 5. The count covers North America with circles 15 miles in diameter. The Allentown circle, centered on Hamilton Boulevard and Route 100, will count for 24 hours Dec. 17; the Hellertown-Bethlehem-Easton circle will count Dec. 31.

The CBC began in 1900, when ornithologist Frank Chapman encouraged his friends to count birds on Christmas Day instead of taking part in a traditional hunting contest. According to the national Audubon Society, Chapman’s initial 27 birders counted 90 species across the continent-from Toronto, Ontario, Canada, to Pacific Grove, Calif.

Each year since 1900, CBC coordinators have plotted paths for bird-counters to follow, performing a wintertime bird census of North America. This year, tens of thousands of bird-counters are expected to participate. Compilers tally the results for each circle. Counters and compilers follow a rigorous methodology, as data from the CBC are used by academics and government employees to inform research and policymaking.

Brandon Swayser is the volunteer coordinator of the Allentown circle, which is divided into 12 area teams, each with a leader. Leaders can identify any bird they see or hear by sight or sound, Swayser says.

Elaine Mease coordinates the Hellertown-Bethlehem-Easton circle, which will have between 12 and 15 teams, in addition to feeder-watchers. Mease expects between 50 and 75 volunteers to count 80 or 90 species of birds. She notes that bald eagles used to be a rarity, but the population has rebounded. More common birds, like crows, will number in the thousands.

Swayser enjoys being part of the CBC because of the opportunity to see rare birds, as well as the national importance of the project.

“The most intriguing part to birders,” he notes, “is that when you are birding for 12 to 18 hours straight and covering a large area, you tend to find some unusual birds.” The Allentown circle, he adds, has been counting since the mid-1940s.

From its small beginnings, Swayser explains, the CBC “has become one of the biggest conservation tools we have, because how often do you survey anything in the same place year after year? It has shown us all sorts of trends. […] That’s the magic of citizen science; you get thousands of amateurs to collect data in an organized way.”

Birders who want to get involved in this year’s count should contact the circle volunteer coordinator listed on the Audubon Society website (https://www.audubon.org/conservation/join-christmas-bird-count), which is updated every November. Expert birders can also volunteer as feeder-watchers if they live within a circle.