Thomas Bancroft describes findings of 2009 citizen scientist winter bird count
Every winter, people in North America are encouraged to go outside and count birds, for science. EarthSky spoke with Thomas Bancroft, Chief Scientist with the Audubon Society, about what’s known as the Christmas Bird Count.
Thomas Bancroft: The Christmas Bird Count is the largest citizen science program in the world. It involves roughly 30,000 people every year, who put in almost 60,000 people days of volunteer effort to count birds across the United States, Canada, and expanding in Latin America.
Bancroft said that – over the course of a few weeks – volunteers survey birds out in the field. He added that many also monitor their bird feeders to keep track of winged creatures traveling by.
Thomas Bancroft: What’s been exciting about it is National Audubon is trying to use this information, over the last 15-20 years, to talk about the status of birds. So we’ve done a series analysis and released a series of publications. One we did in 2007 was on common birds in decline.
Bancroft said volunteers discovered a significant decrease in several bird populations.
Thomas Bancroft: We were shocked to find 20 of them had decreased by more than 50 percent in the last 40 years. So things like bobwhite quail, evening grousebeaks, and northern pin-tail ducks, and greater skops. So there are a lot of things that have gone down.
Bancroft said that other birds, like wild turkeys and collar doves, have actually gone up in numbers thanks to conservation. And, thanks to people who count birds, this information is known and shared with scientists.
Thomas Bancroft: People should really feel good about this. It’s something that we couldn’t do other than by volunteers. So it’s a really exciting thing that happens.
Dr. Bancroft spoke more about what people do at the Christmas Bird Count.
Thomas Bancroft: It’s open to everybody to participate. Each Christmas Bird Count is organized by a local compiler, a local coordinator. Each circle is a 15-mile diameter circle. People divide up that circle into different sectors. Each sector gets assigned a party, usually one to four people, who go out and spend the day looking for birds and trying to count all the birds they can within that area. A person who wants to volunteer needs to find out when the circle is going to be counted in their area. It’s a single day between the 14th of December and the 5th of January.
There are good reasons, said Bancroft, why the bird count happens in the chilly months for North America of December and January.
Thomas Bancroft: In the 1800s, a common pastime for people would be to set up teams and go out on Christmas day and see how many birds they could shoot in the day. And so in 1900 Frank Chapman, who was an ornithologist in the American Museum of Natural History in New York, tried to figure out how can we stop people from going out and killing birds and let’s see if we can get people to go out and count them instead. He organized the very first Christmas Bird Count in 1900, in which 25 people went out and participated in a dozen or 15 places across the country and tried to count birds, and then see how many they saw in that time. And that has simply grown from that original 25 people in 1900 to now almost 60,000 people-days worth of people going out and counting across the country.
Data from The Christmas Bird Count and others shows climate change is affecting birds, said Bancroft.
Thomas Bancroft: One of the neat things about this count that’s done all over the United States and Southern Canada is that it gives you a snapshot every year of where are birds in the early part or winter. So what we did was we looked at that for 305 species that had good coverage across the United States. We looked at what was their center of abundance each of the last 40 years, back in 1966.
Bancroft noticed a shift in bird distribution.
Thomas Bancroft: And what we were able to show was that for a little over half of them, a little bit below 200 species, we saw a shift in their distribution North over that 40 years. Now it wasn’t an incremental shift a little bit every year. It was, some years they went up a little farther south, when it was more cold. Some years they stayed up a little farther north. But over that 40 year time span, there was a shift north in the distribution of birds. So there’s a clear indication that with the gradual warming temperatures of the last 40 years, birds have been able to stay farther north than they had been in the past and occupy different habitats because of that.
For more about how to participate in the Christmas Bird Count, see this link to the Audubon Society’s Christmas Bird Count.