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The killing games were coming to an end. At the turn of the 20th century fewer sportsmen were participating in bygone Christmas Day “side hunts,” competitions in which hunters would split into teams and set out on a “cheerful mission of killing practically everything in fur or feathers that crossed their path,” as ornithologist and editor Frank Chapman described in the pages of Bird-Lore, the precursor to Լ����Ƶ magazine. “We are not certain that the side hunt is wholly a thing of the past, but we feel assured that no reputable sportsman’s journal of today would venture to publish an account of one, unless it were to condemn it; and this very radical change of tone is one of the significant signs of the times.”

Chapman had a : Replace the side hunt with a new tradition of observing and tallying birds, what he called a “Christmas bird-census.” He urged readers to mail their “hunt” report to Bird-Lore’s Englewood, New Jersey, office by bedtime on Christmas. The reports should include the locality, when the count began and stopped, the air temperature, the character of the weather, the direction and force of the wind, and the total number of individuals of each species observed. He promised to publish the results in the February edition of the magazine.  

Responding to Chapman’s call, on Christmas Day, 1900, 27 enthusiastic participants fanned out in 25 locations across the United States and Canada, tallying 89 species in total. From there, the idea spread quickly. Soon the Christmas Bird Count (CBC), as it became known, was being held in every state and across Canada. It even carried on through the height of World Wars I and II, when many people couldn’t participate because they were caught up in the fighting overseas (though a few did submit reports from abroad). 

Today some 80,000 volunteers conduct local counts each year at more than 2,000 sites in the United States, nearly 500 in Canada, and 180-plus in Latin America, the Caribbean, and the Pacific Islands. The Christmas Bird Count has become the nation’s longest-running community science effort on birds and a vital resource for researchers. The program provides data that scientists and wildlife managers use to establish bird population trends, observe how animals are responding to environmental threats, and recommend actions to protect birds and their habitats as temperatures warm, sea levels rise, and human use of the landscape changes. 

“The Christmas Bird Count is one of the most valuable data sources we have for understanding how birds have responded to global change, particularly in North America,” says Brooke Bateman, Լ����Ƶ’s senior director of climate and community science. “The fact that it goes back to 1900 and has been done consistently since then really gives us so much information.”

This trove of information has helped usher in entire new areas of research, like climate change ecology, says Benjamin Zuckerberg, a  at the University of Wisconsin–Madison. His work in the field utilizes large community science datasets to explore how birds, including common winter denizens such as Red-bellied Woodpeckers, Purple Finches, and Carolina Wrens, are shifting their movements in response to changes in temperatures. The data enable scientists to find answers to questions at an “unprecedented” level, Zuckerberg says.

Stanford University retired biologist Terry L. Root, for instance, used data from counts in the 1960s and 1970s to embark on some of the first research into how environmental changes affect birds. When she used the CBC data to examine bird distributions on a continent-wide scale, the influence of climate became clear. The Eastern Phoebe’s winter range, for instance, was restricted to areas where the temperature stayed at 25 degrees Fahrenheit or higher in January. It was a revelation. “I know it seems obvious now that birds’ ranges are limited by temperature, but I promise you: In the late 1980s, that was not obvious,” Root says. “Folks back then thought that competition with other species of birds was what limited species ranges. They could not see the effects of climate when the study areas were so small.”

Since Root’s pioneering investigation, more and more researchers have delved into the data to better understand birds’ movements and factors that influence where they live. A  by the U.S. Environmental Protection Agency based on CBC data from 1966 to 2013, for example, concluded that in that span, more than 60 percent of 305 species moved their wintering grounds north. Nearly 50 of those species shifted more than 200 miles.

More recently, Լ����Ƶ’s science team found that waterfowl populations are migrating shorter distances. Analyzing 50 years of records on 16 common duck species, they found that as winters have warmed, making food and water more readily available, the majority of those species, including Northern Pintails, American Black Ducks, and Northern Shovelers, have become more common in the north and less common or stable in their traditional southern wintering grounds.

CBC data have also revealed that changing land use, such as draining wetlands for development and plowing grasslands for farming, is likely having an even greater influence than climate change on species that require specialized habitats, such as waterbirds, grassland birds, and waterfowl, Լ����Ƶ scientists reported in 2022. They discovered that over the past 90 years, alterations to the habitat that these birds depend on have accelerated across nearly 120 CBC circles. One-third of midwestern grasslands were converted to croplands, and two-thirds of Atlantic and Gulf Coast wetlands were drained and ditched for urban development. “There’s this tug between climate and land use across the species’ range,” Bateman says—a finding that may not have been detectable without the CBC.

More discoveries are inevitable, especially because the data are available online and readily accessible to scientists worldwide—a relatively recent development. When Geoff LeBaron started as CBC director in 1987, participants received a 16-page booklet to record count information, then mailed it to Լ����Ƶ, along with a fee to fund the publication of the results—a phone-book–like tome consisting of up to 700 pages.

With the digitization of the archives in 2000, the program entered the modern computing era. The CBC is evolving in other important ways, too, says LeBaron, who recently retired: “We need to keep monitoring the birds, but we also have to think about who’s doing the monitoring.” 

To that end, the CBC is expanding to encompass more places and people not historically represented in the program—including Latin America, where hundreds of migratory bird species overwinter. Last year alone saw 16 new CBCs in Cuba, 5 in Colombia, and more throughout the region. The effort goes beyond geography. Making the CBC more welcoming will help diversify participation, says Gregoriah Hartman Ruh, Լ����Ƶ’s director of network action and leadership development. While many backyard bird enthusiasts have the skills to take part in a CBC, Hartman Ruh says, they might not have felt drawn in yet by their local Լ����Ƶ chapter or birding club. And some people don’t participate in events like the CBC because they feel unsafe; often birders are in remote locations, away from a car, without a quick escape route, ze explains. It’s something Hartman Ruh experienced when in the field alone, but not when out with a group of trans birders: “We felt safe together.” The key to making the CBC more inclusive, Hartman Ruh says, is to break down the stereotype of a birder, which an increasing number of Լ����Ƶ chapters and CBC counts are striving to do. 

In Manhattan, the site of one of the inaugural counts in 1900, the (formerly NYC Լ����Ƶ) has made equity, diversity, inclusion, and accessibility central to its mission to engage more people with birds and nature. For this year’s CBC, the organization is pairing experienced data compilers with new volunteer engagement leaders who will help ensure “no one’s getting left behind, that there’s someone there who can help answer questions and make sure that everyone is having fun,” says Katherine Chen, who manages the group’s community science programs. The group also plans to add more “slow birding counts,” similar to one that launched two years ago in Madison Square Park, providing an opportunity for those with physical impairments or who require a slower pace. They are also hoping to introduce bilingual counts and new counts in areas that haven’t been previously represented. “We do this because birding is and should be for everyone,” says NYC Bird Alliance executive director Jessica Wilson, “and because it will take everyone involved to protect birds from the effects of climate change and biodiversity loss.”

That’s also the motivation driving the Լ����Ƶ’s efforts to make the CBC more multicultural and multigenerational. The organization is partnering with researchers on a National Science Foundation–funded pilot program, called IDEAL, aimed at increasing involvement among new birders and within communities underrepresented in the tradition. This past summer 16 CBC leaders from 11 count circles took part in trainings where they thought expansively about how to recruit new participants—ideas that they are now implementing.

Lauren Whitenack is the vice president of in northwest Nevada and chair of the organization’s equity, diversity, inclusion, and belonging committee. After participating in the IDEAL training, she distributed a demographic survey to Christmas bird counters in Reno to better understand who has been excluded or underrepresented in the past. One finding: There were no participants from the LGBTQIA+ community. Now the Լ����Ƶ chapter is forming an advisory committee made up of members from that community who receive a small honorarium for their time and expertise and a free one-year membership to the organization. This year, the group’s CBC will offer multiple ways for new volunteers to get involved, including a group walk geared toward beginners at a local park and compilers buddying up with participants taking part for the first time.

Inclusion isn’t about teaching more types of people to enjoy birds, says North Carolina State University ecologist Caren Cooper, who is collaborating with Լ����Ƶ on the IDEAL program. 

“Inclusion involves changing the project environment so more people feel a sense of belonging, rather than keeping everything the same and asking people to change in order to fit in,” she says. “If we are inclusive, then the love of birds can unite people.” The CBC of the future might look a little different than in the past, but it will provide even more rigorous data, across more areas, if a wider variety of people are collecting the information, Cooper says.

Chapman likely never imagined that his 1900 plea for people to count instead of kill birds would expand to such proportions. From its humble beginnings, the Christmas Bird Count has become an indispensable tool for understanding bird populations and trends and helping to protect species and habitats—and it will grow stronger with each new year, circle, and volunteer. 

This story originally ran in the Winter 2024 issue as “All Together Now.” To receive our print magazine, become a member by .