Participating in the Christmas Bird Count Is Good for Science

The Christmas Bird Count (CBC) is one of the oldest and most well-known bird focused community science programs globally. Dating back to 1900, the CBC was started by Frank M Chapman who encouraged fellow birders to count, rather than hunt, birds across the US and Canada every year around December. Thus, a new tradition of bird ‘counts’ was born that has grown in popularity and has served as model for community science programs around the world. That first year, 27 people that participated across 25 locations tallying more than 18,500 birds, representing 89 species. Now, the CBC has grown significantly with over 80,000 observers that participate each year, counting over 40 million birds annually across the western hemisphere. Audubon has been the proud overseer and caretaker of this invaluable bird dataset. The success of the CBC is rooted in tradition and on connection between people and nature, on sharing the love of birds on the count day with longtime friends and new birders. But there is also a solid consensus of the importance of CBC data in our understanding of birds across the Americas.  

The long-term nature of the data collected during the CBC allows us to understand how bird communities have changed over time. Audubon scientists have been able to analyze population trends for bird species over several decades, giving us insights into how each species is faring. Indeed, across North America birds are not faring well. A 2019 study analyzed CBC data along with other datasets to come to the grim conclusion that we have lost nearly three billion birds, an equivalent of one in four birds, since 1970. Canada’s 2024 State of the Birds Report, echoed similar losses, identifying steep declines in grassland birds and shorebird species. CBC data were integral in both studies. 

Across the 125 years since CBC commenced, we have seen dramatic changes in our climate and devastating habitat loss across most ecosystems. These changes include increasing temperatures leading to milder winters and earlier springs, shifts in rainfall patterns such as strong droughts and increase heavy rainfall events, and strong shifts in habitat from increased urbanization to loss of natural grasslands, wetlands, and forests. 

 Given that birds are intimately connected to the environment around them, having information on birds that span the 125 years allows us to test the relationship between bird species population trends and such environmental factors as climate and habitat change. In one such study analyzing 90 years of CBC data in the eastern US, Audubon scientists revealed that local climate dictated where bird species were able to live over time, but changes and loss in habitat had a strong impact on species like grassland birds and waterbirds that require specific habitats. Over that time, as climate and habitat conditions changed, so did the populations and distribution of the birds in those places. In another study led by Audubon scientists, there was strong evidence linking climate change with range shifts and expansions by important dabbling and diving game duck species. Overall, duck species are spending more time in the northeastern US, expanding into areas that are experiencing warmer winters, indicating some species are overwintering in more northly locations forgoing their traditional southern migration. The implications of these studies reveal that our bird communities are changing, they are responding to the drastic changes in climate and habitat we have seen in that last century and a quarter, and we know this because of the wealth of data provided by the CBC.  

There are more than 300 scientific publications based on CBC data, on topics ranging from bird species diversity, population trends, habitat impacts, distributions, range shifts and more, highlighting the ever-growing scientific importance of the data collected each December and January.  

In the 1950s, it was stated about the CBC that "One has the feeling that there is more gold buried in the mass of data than has yet been uncovered.” As a scientist reflecting on this statement, I think this resonates even moreso today.  It’s hard to know if those first 27 individuals knew the significance of what they started back in 1900, but I do think it’s safe to say that any CBC participant taking part in the tradition of counting birds for the joy of it, can also know they are serving as an important part of our scientific understanding of birds today. The value of every volunteer of CBC to conservation, to birds, and to science, is worth its weight in gold. 

As I take the reins of this incredible community science project and winter tradition, I’d like to thank all CBC participants of the past, present and future. You are helping Audubon protect birds and the places they need across the Americas.