Portland Christmas Bird Count 2017 along the Eastern Trail at Scarborough Marsh Photo by Ariana van den Akker courtesy Maine Audubon

This winter marks the 125th anniversary of the Christmas Bird Count. We tend to get a range of questions each year, ranging from “What is it?” to “How can I take part?” to “Is it even necessary in the modern digital era with projects like Cornell’s eBird?” So this week I wanted to cover the basics and share some of the findings from this project, and at least give one quick answer: yes, it is still necessary!

Let’s start from the beginning: 125 years ago, Frank Chapman, an American ornithologist, proposed the idea of changing a Christmas tradition called “side hunts” from a challenge of seeing who could shoot the most birds to simply counting them. That year, there were only 25 counts with 27 people participating, but it has since grown to more than 2,300 counts with more than 70,000 participants. Instead of just being on Christmas Day, the counts are now held between Dec. 14 and Jan. 5. Each count covers an area defined by a circle 15 miles in diameter, and that is typically broken up into sections. Various teams of volunteers will spend the day attempting to count every bird within their section. At the end of the day, each count compiles all the section’s totals (a process run by each count’s official “compiler”) to get the final numbers for that count in that year.

This is when someone usually pipes in with “how do you know you counted ALL the birds?” or “how can you tell a bird didn’t move into a different section?” but that is one of the convenient parts of a large-scale community science project like this. It doesn’t matter! It is impossible to count every bird and keep track of each individual. Each year the effort will change, too – there might be more people participating, or the weather may be terrible. But trust me, this is all tracked (reported by the observers) and accounted for. We account for changes in effort by looking at an effort-weighted measure called “birds per party hour,” which divides the number of each species seen by the total hours spent looking, so larger or smaller groups or longer observation times don’t unfairly skew the results. The greatest value in a project like this is doing it over long periods of time and large areas of space, so if you are still concerned about no one counting that single chickadee in your backyard this year, know that they probably didn’t count it last year either. My favorite oversimplification of this non-problem is “as long as you do it wrong every year, you’ll still identify the trends.”

The Christmas Bird Count helps to learn trends in the bird population. Photo by Ariana van den Akker courtesy Maine Audubon

Speaking of identifying trends, in January 2022 a study was published that examined the results of 90 years of changes in bird populations using Christmas Bird Count data. Published in the journal Global Change Biology, Sarah Saunders et al sought to break down the factors contributing to changes in bird populations. I encourage you to give “Unraveling a century of global change impacts on winter bird distributions in the eastern United States” a full read, but let me summarize some key points for you. On the spatial side, they were able to determine that the areas where a group of species occurred was most explained by climate, looking at minimum temperatures and cumulative precipitation in those areas. On the temporal side, changes over time were most directly attributed to changes in land-use/land-cover, especially for habitat-constrained species like grassland birds and waterbirds. To quote from the paper’s authors: “Effective land management will be critical for improving species’ resilience to climate change, especially during a season of relative resource scarcity and critical energetic trade-offs.” I thought this was especially important to point out. While climate change is the greatest threat we need to combat, we also must make sure we are protecting the habitats that birds use.

In Maine, most of the counts are scheduled early in the count period, which begins on Dec. 14. Some counts are small and may not be the easiest for a large number of new people to join, but you can find a list of all the counts in Maine, the dates they are being held, and their coordinators on Maine Audubon’s website, maineaudubon.org/cbc. Contact the coordinators for more information.

Have you got a nature or wildlife question of your own? It doesn’t have to be about birds! Email questions to ask@maineaudubon.org and visit www.maineaudubon.org to learn more about birding, native plants, and programs and events focusing on Maine wildlife and habitat. Doug and other naturalists lead free bird walks on Thursday mornings starting at 8 am, at Maine Audubon’s Gilsland Farm Audubon Sanctuary in Falmouth.