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People have been counting birds on Christmas for 115 years. Here's what we've learned.

Cardinals are one of the hundreds of species of birds that can be found in the winter.
Cardinals are one of the hundreds of species of birds that can be found in the winter.

This holiday season, some 70,000 people will locate themselves within one of more than 2,300 15-mile-wide circles and then, for the next 24 hours, try to count every single bird within it. This is the Audubon Christmas Bird Count, the longest running census of animals on Earth.

The Count — which started in 1900 and this year technically runs from December 14 to January 5 — has accumulated data that's led to hundreds of scientific studies about the health of our birds and their ecosystems. For example, this fall, the National Audubon Society used its database to predict that climate change is threatening half of North America's birds.

I talked to Gary Langham, Audubon's chief scientist, about what researchers have learned from more than 100 years of avian records — and why people continue to sign up to find birds outside, in the freezing cold, for hours and hours on end:

Susannah Locke: How did the Christmas Bird Count start, and what has it grown into?

Gary Langham: The Christmas Bird Count started in 1900, so this is the 115th year that it’s been going on. It was an idea by Frank Chapman, [who] worked at the American Museum of Natural History at the time. What he realized was there was this tradition of the "side hunt" that people did around Christmastime, where they got done eating and had a contest to shoot everything that flew or crawled or slithered. And then whoever had the biggest pile of dead stuff was the winner.

What Frank realized was that was crazy and that maybe we could still have that tradition of going outdoors, but instead of shooting stuff, let’s count things. And that was the beginning of the Christmas Bird Count.

Today it is now the longest running animal census in the world and has more than 70,000 people volunteer their time to go out and count birds each year.

When you look at community-level activities in the United States, they’re actually in serious decline — like bowling leagues aren’t nearly as popular as they used to be. And yet somehow, the Christmas Bird Count keeps growing in participation every year. I think the secret to success is that it’s really local. It’s the fact that people really care about where they live, and they welcome the chance to get outdoors.

SL: How important is this 115-year-old database of bird sightings for scientists?

GL: It’s a tremendously valuable resource for researchers. Having this long-running census gives us an idea of how birds are faring. It really helps us understand where birds are declining, when conservation works and when they’re doing better, and to have really the pulse — not only of birds, but of ecosystems in general. Birds are a great indicator of overall environmental health.

SL: You recently released a huge report about how birds could get messed up by climate change. What did you find?

GL: Just this last September, we released the Audubon Climate Report, which was based on information collected during the bird count and its corollary run by USGS in the springtime. So we had two snapshots of how birds were doing: one in winter and one in the spring and summer.

We combined that with climate variables to get a sense for how birds were related to their climate. Then, we could project onto the future how sensitive each bird is to shifting its range or being impacted [because of climate change].

And the bad news is that 314 out of the 588 bird species we looked at in North America are seriously threatened by climate change, unless we take urgent action.

SL: What other important scientific findings have come out of the Christmas Bird Count?

GL: There are hundreds of published studies that have drawn on [the] Christmas Bird Count, and a couple times a month we get requests from researchers asking for the information.

There's The State of the Birds Report — sort of a snapshot of the health of birds in North America. Things like State of the Birds are great because they help to direct and inform on-the-ground conservation efforts.

Other examples are looking at how bird ranges have moved over the last 40 years in response to increasing winter temperatures from climate change. The EPA uses this analysis as one of their climate indicators. What we found was that 60 percent of them had moved the center of their ranges north by at least 30 miles. The climate we’ve already experienced — the warming of winters — is already showing up.

Another example that Audubon has done is something called Common Birds in Decline, where we showed that even with [common] birds like robins and meadowlarks, huge numbers of birds have declined tremendously over the last 40 years.

SL: Does the database show the effects of other threats, like pesticides?

GL: Yes. Part of what caused the mainstream environmental movement was the realization about things like DDT. And one of the things that we could see in the Christmas Bird Count numbers back then were that bald eagles and peregrine falcons had a massive decline. They were headed for extinction. Because DDT makes their eggshells thin, so when the adults sit on the eggs, they crush them.

This is a good story, believe it or not. When people came to their senses and banned DDT in the United States, there was a very obvious uptick in bald eagles and peregrine falcons. And today, both of those species are now off the endangered species list.

SL: Is there any other good news about birds?

GL: The latest State of the Birds report shows that most groups of birds have actually been increasing recently, particularly in areas where there has been a lot of focus, like wetlands. We had converted 95 percent of wetlands to agriculture and development. Then, hunters and conservationists and agencies got together at the turn of the century and bought and restored wetlands. And those birds have responded really well.

The negative side is that climate change is coming and threatens to undo all these conservation successes. At the same time, our history tells us that when you give nature and birds half a chance, they can and do respond positively. So there’s also a lot of hope that we can do the right thing.

SL: I've heard that birding is one of the most popular hobbies in America. How big is it, really?

GL: People self-report that their number one hobby is gardening. And the second is birdwatching. So 58 million people in the US say that they like to watch birds. And that seems a little surprising, maybe, at first. But I will bet you that someone in your immediate family feeds birds in their backyard and has binoculars.

[And then birding goes] all the way up to the "listers" [people who keep lists of bird sightings], who will drive 14 hours to see some bird that accidentally flew across the sea from Europe or something. There’s quite the range.

SL: Why do you think birding is so popular?

GL: People appreciate being connected to nature. And pretty much every person sees or hears a bird every day. And then, compared to mammals and things — those are harder to get in touch with. Birds are just around, and we see and hear them all the time.

SL: What’s one of the most exciting things that people might spot this year?

GL: Things that people get excited about are things like, what’s likely to be this year, a snowy owl invasion. These beautiful, white-and-black spotted birds are coming much further South than they normally would.

SL: Is there anything new about the Christmas Bird Count that you can share?

GL: In some ways, we’re still doing it the same ways we did in 1900. And yet, there are new questions that come up. Like this year, people are asking us is it OK if they count birds that they see with a drone, for example. Or what if they just record something and watch it later.

SL: But you need methods to be fairly consistent from year to year for comparison purposes, I’m guessing. You don’t want to over-count just because you have a drone, right?

GL: The answer is no, you can’t use a drone, for now. And the [other] answer is yes, if you want to set up a microphone and listen to it live, that counts.

This interview was condensed for length and clarity.

Further reading

Climate change threatens half of bird species in North America