Inside the Data Factory

So you’ve participated in a Christmas Bird Count or have signed up for a few Climate Watch blocks. You’ve sent in the data and now you have questions about who analyzes that data and what are they looking for. Well, we have some answers. American Birds spoke with quantitative ecologists Tim Meehan and Sarah Saunders, and Audubon’s Director of Climate Science Brooke Bateman, about their work with your hard-won data points.  

Meehan, who is a quantitative ecologist with Audubon’s Science team, spends his time digging through the vast datasets of the Christmas Bird Count. Now in its 122^nd year, the Christmas Bird Count is one of the longest-running community science projects in the world, and the data collected is some of the richest available for avifauna in the Western Hemisphere. 

What are some of the ways in which data from the Christmas Bird Count are used?  

Some folks use the data to answer basic science questions about how birds interact with each other, other species in their community, and their physical environment. Other folks use the data to understand how birds respond to more recent changes in the environment caused by humans, things like habitat degradation and climate change. And yet other folks use the data to judge if species are increasing or decreasing in different regions, and if current resource management policies are helping or harming birds. The CBC database is remarkable in that it goes back more than one hundred years and covers a whole continent! And that scope is growing every year. The questions you can ask of the data are only limited by your imagination.   

Tim, you periodically update the population trends of some birds using data from the Christmas Bird Count. What does a bird population trend tell us?  

Every couple of years, the Science team pulls together the latest CBC data and updates population trends for more than 500 species of birds. These population trends tell us how each species is doing. Are the numbers stable? Are they increasing or decreasing? Maybe they are increasing in one part of their winter range but increasingdecreasing in another part.   

We produce two kinds of trend reports: long-term trends that cover approximately 50 years, and short-term trends that cover the last decade. We produce them for individual states and provinces and whole countries. When we are done, we put all these trend reports on the Audubon website so that anyone can view them, download them, use them in whatever way is helpful.   

A lot of people use them, too. Some folks visit the site just to see how species are doing in their area, because they are curious. A lot of scientists download the trends to do their research. One recent example that comes to mind is a scientist who is using the trends to understand how birds have shifted their winter ranges in the last few decades due to warmer winters. Other trends customers are wildlife biologists that work with Partners in Flight and Environment Canada, who use them to inform management recommendations.   

How long does your process take to run these population trends?  

From start to finish? Well, first it takes about seven months, on and off, to get all the data entered, verified and cleaned up. Geoff [LeBaron, director of the Christmas Bird Count] mostly does that. Then it takes me about five months, on and off, to do the trend analyses, do a bunch of quality checking, get them bundled up for public consumption, and sent off to folks who put them on the Audubon website.  

What is one thing about Christmas Bird Count data that you think would be a surprise to volunteers?  

I’ll bet that people would be surprised by the power of CBC data. Every year I get data requests from scientists in Canada who study birds of special conservation concern. CBC data are regularly used to evaluate the conservation status of the ‘snowbirds’ that breed in remote parts of Canada, where they are hard to monitor, but winter in the USA where they can be counted by CBC volunteers. Bird conservation status, whether it is threatened, endangered, special concern, or otherwise, can have a huge economic impact on many thousands of people.   

What’s one of the weirdest things you’ve seen in the data? 

Over time, one of tThe most abundant species counted on CBCs has been Red-winged Blackbirds—they account for up to one-third of all of the 4.7 billion birds that CBC volunteers have tallied since the CBC began. But one memorable year—the 88^th CBC, according to Geoff LeBaron—birds, and especially Red-winged Blackbirds, thronged topiled into one count circle in Pine Prairie, Louisiana. That year, volunteers counted more than 100 million birds—more than all birds counted by all the other count circles combined—53 million of which were Red-winged Blackbirds.  

Sarah Saunders, also a quantitative ecologist with Audubon’s Science team, analyzes the data generated by volunteers for Climate Watch, Audubon’s newest community science project. Together with Brooke Bateman, director of climate science, Saunders aims to track how birds are—or aren’t—responding to a changing climate. While the program is still quite new, Saunders and Bateman are already seeing some bird species responding to the changing conditions around them. 

Sarah, how is Climate Watch data used to understand birds and a changing climate?  

There are two important ways we use Climate Watch data. First, we use the observations to determine whether our climate suitability predictions are correct. Are species being found in locations that are predicted to be more climatically suitable than those that are not? If they are, then we know that the models we build to predict where climate conditions will become more or less favorable are indeed accurate.  

Second, once we’ve validated the climate predictions, we use the observations to see whether species really are moving in response to changing conditions – are individuals leaving locations that are worsening in suitability and moving into new locations that are becoming more suitable? In other words, which species seem to be doing a good job of tracking climate change? Which species seem to be “stuck in place”, or remaining in locations that are worsening in terms of climate suitability? 

How many data observations are really needed in order to tell us if the birds are moving their ranges?  

Answering big questions like range shifts requires a lot of data! Not only is it important to have observations from across species’ ranges, but it is critical to have observations over a long period of time. Species’ occurrences can change each year in response to local weather conditions or land use, but that doesn’t necessarily mean their entire ranges are shifting. Generally, range shifts can only be detected after decades of data collection.  

What happens if a particular location is only surveyed for two years? Can the data still be used?  

Yes! That’s the beauty of a large community science program like CBC or Climate Watch. We pool all the observations across the country each year to get a bigger picture of what is going on, which means if a site “blinks” on or off between years, that’s ok because we can still understand the larger patterns when all the observations are combined.  

Brooke, one of the important things about Climate Watch is documenting where birds are *not* found.  Is it hard to get people to look for birds where they’re not supposed to occur?  

Most birders don’t like missing seeing a bird. But experiencing the frustration of “dipping,” the act of searching for a bird and not finding it, is incredibly important to the science of Climate Watch. Why? Because some of these bird species may not live in a particular area now, but they could move into that area soon because of climate change.   

As such, those ‘zero’, or absence, data points help us understand where a bird species is or isn’t right now—and we can track how that will change over the next five, ten, or fifteen years. The same goes for when you detect a species for several years at a location, and then they disappear. Over time we can compare the bird data with our climate change models to determine if and how climate change is causing these shifts. I think once volunteers understand the importance of how not finding a bird contributes to our broader understanding of birds and climate change, they’ll be more willing to put up with some missed birds on their birding trips.   

I spent several winter Climate Watch survey periods looking for Eastern Bluebirds in Madison, Wisconsin. The climate conditions are expected to continue to improve for this bird in winter there, and there have been more found each year as time goes by. Most years I didn’t find any bluebirds on my surveys, but one year I did which was really quite exciting. It helped me feel that my being there, looking for these birds year after year, I was contributing to our understanding of how a global scale problem like climate change can affect birds in my neighborhood.    

Speaking of Christmas Bird Count, Sarah, you’ve done your fair share of analysis of that dataset. With a dataset that large and varied, when you look at the much older counts, do you have to do things differently than just doing studies on the more recent data?  

Yes, often with long-running community science programs like CBC, survey protocols have changed over time. In order to analyze all the data (both historic and recent) consistently, those varying protocols and efforts need to be accounted for during analysis. Frequently, we can do things like correct counts of species based on the amount of effort or sometimes, we will start the time period of analysis at a certain point after more consistent protocols have been in place. In other cases, we can analyze time periods separately and then compare results. For example, if the first few decades of a dataset followed one protocol but the most recent decades followed another, we can analyze those two sets of decades differently (accommodating the different protocols) and then standardize the results in way that they can be compared to understand any differences in counts (or whatever is being measured) between historic vs. recent time periods.   

Tim, do you have more fun analyzing Christmas Bird Count data, or participating on a CBC?  

Analyzing the data. I know. I’m a geek.