What Are the Birds Telling Us About Climate Change?

Reading the signs from our friends up in the sky


Jane Tillman, Ken Zaslow, and Skip Mencio on the lookout at the Christmas Bird Count in South Austin (Photo by Jana Birchum)

A conversation alfresco with a passionate birder is likely to be interrupted by the birds nearby. Jane Tillman, a master naturalist and one such birder, will often break mid-sentence, mid-phrase, even mid-word, at the sight or sound of a bird. When this happens, she may abruptly lean back, hand shoved into her back pocket to brace herself, as she points her hat brim to the sky and scans for what she has just heard or sighted.

I met Tillman early one cold morning in mid-December for the Austin Christmas Bird Count. She was our group leader and that much was evident upon arriving at our meeting point – the H-E-B parking lot on East William Cannon. It was 7am, and we were there to count the grackles. You know the grackles; they dot telephone wires around town and their large flocks sometimes perform arabesques across the sky. You might mistake them for crows, but they are not. Counting the grackles is kind of a joke to the birders, but not completely. Just before sunrise, the inky birds are relatively still around the parking lot. Our group estimated how many per wire, performed some quick multiplication, added in others in the sky and just beyond the lot, always aware of our group's boundaries, to account for about 3,500 grackles. This total went into our official tally.

Counting the grackles is kind of a joke to the birders, but not completely.

Every year around the holidays, small groups of volunteers count the grackles and any other birds they see in participation with this international citizen science project, sponsored by the National Audubon Society. Originally conceived at the onset of the 20th century, the Christmas Bird Count is an adaptation of a much older avian tradition. Previously, hunters would engage in a competitive bird hunt around the holidays, aiming to bring in the most feathered kills. Then ornithologist Frank M. Chapman had the wild thought: Instead of shooting the birds, why not count them? Since 1900, birders have done just that, and the results have provided remarkably extensive sets of data on bird populations. This data has been used to study long-term developments of migratory patterns and population trends. Ecologists frequently point to the unique advantage the data sets from hobbyist birders provide in tracking wildlife response to habitat loss and climate change.

Frank La Sorte, an ecologist at the Cornell Lab of Ornithology, regularly uses citizen science data in his research on birds and climate change. "Birds are easy to observe, and you have this large community of people who enjoy observing birds," he says. "So, we get a wealth of data. Birds are the best-studied taxon or group of species in the world.

"Another thing is they're highly mobile. So, if there's a change in environment, a change in land cover, a change in temperature, precipitation, birds can move to accommodate that. So, they're very useful for scientists. Information has been gathered across time, so we can chart that data."

Well, what are the birds telling us? It depends on the species. "You have birds that are resident birds, that are here year-round; birds that are short-distance migrants, they'll move from Canada to the United States or Mexico; and birds that are long-distance migrants, they'll move from Canada all the way down to South America," says La Sorte. "And each of those birds are functioning under a different set of parameters across the year, and they have cues that tell them when to do certain activities, and as the climate changes, each group is responding." The annual count tries to systematically record them all.

The Early Birds

After the grackles, we embarked on the rest of the count in earnest, packing into vehicles bound for Kendra Page Park. I joined Tillman and Skip Mencio, who'd recently retired from computer software work and has been birding since his first bird watching experience at a count, many years ago. "I liked being outside," said Men­cio. "I was a zoology major in college, and the guy who sat across the aisle from me on a cubicle farm invited me on a Christmas Bird Count. Then I started a little bit here, a little there. It's a great and inexpensive hobby. After you've got the binoculars, it's just a matter of getting up early in the morning."

Birders are early risers. They are also astute observers. Excellent describers, birders are able to specify exactly which shade of brown plumage they saw; where on the body to find a stray identifying marker; where along the tree line to point your binoculars; and the distinction between one bird's caw and another's chatter. They are also awfully hardy. The temperature stayed in the 40s all day, and once the thick woolen blanket of clouds overhead finally began to seep rain in the early afternoon, it didn't stop. My jacket did little to keep out the wet, and lifting binoculars quickly became futile, as droplets obscured the lenses. That didn't stop the mission: That day, we were to tally birds sighted within our designated area – Area 11 of 13 areas – and so we stuck with the program.

Our next stop was Onion Creek Park, still the morning. Tillman introduced the area: "This is the old flood plain. So they've closed it off and they're buying up people's houses, and it's turned it into this nice, open sp– hey, look there!"

A hawk swooped by and landed on a stump. "That's a nice look. It's a red-tail. It's a young one. It's got a yellow eye."

Mencio noted how the hawk bore stripes on its tail.

"Yeah, but it's got a red tail," said Tillman. "It's not a red-shouldered, which is what you're thinking, maybe. He's got a belly band. You don't think so?"

"I'm not so familiar with the younger ones."

We entered a red-tailed hawk into our tally.

Man-Made Problems

Dr. Camille Parmesan studies wildlife response to climate change from her research and teaching positions at the University of Texas and Plymouth University in the UK. She focuses primarily on butterflies, but is well-versed on how these effects may be and are extending into bird populations.

"The trouble with humans driving climate change is it's not that we have 0.8 degrees centigrade of warming, and then it staying there," she said. "It's constantly changing. That's one of the most difficult things for wild species, is that their target is constantly changing. So maybe they can adapt even quite rapidly. But if the climate is changing faster than they can adapt, then they're never again going to evolve to be in sync with the maximum number of resources. And that is one of the big conservation problems, that it's a moving target."

The National Climate Assessment, published in 2014, summarizes the current and predicted effects of climate change across the United States. The report goes into detail on regional threats, one of which is storms on the Texas Gulf: "Texas' Gulf Coast averages about three tropical storms or hurricanes every four years, generating coastal storm surge and sometimes bringing heavy rainfall and damaging winds hundreds of miles inland. The expected rise in sea level will result in the potential for greater damage from storm surge along the Gulf Coast of Texas."

Since 2014, Texas has seen seven tropical storms or hurricanes, most recently the Category 4 Hurricane Harvey, whose damage is still being measured and processed. In late August last year, the storm drenched the Gulf region. The National Weather Surface added two new colors to its rain index. The cataclysmic event was unignorable and scientific consensus ascribed the severity of its violence to anthropogenic, or human-originating, climate change.

"It's not like wildlife hasn't dealt with extreme events before; of course they have," Parmesan explained when I asked her about the effects of such events. "But you normally have several years or even decades in between these extreme events, so you allow those numbers to recover. Then you get hit again, but by then the population is high enough that you're not causing the population to go extinct. But as these events get more and more frequent, you don't get the recovery time, and then the populations have a much higher likelihood of going extinct rather than just their numbers going down."

Following Harvey, the species tallies at counts along the coast were unsurprisingly down. The storm had indiscriminately flooded and destroyed lives and homes, local wildlife not excluded. Salt marshes were flushed with rainwater, trees where songbirds gathered were demolished, and coastal habitats were eroded. The Port Aransas boardwalk where the local CBC group typically gathers was wiped out, something Mencio recalled seeing on a recent visit to the coast as we settled in for lunch during the count.

"Down at the coast, just the reports they're seeing now, the number of species is down, but also the number of individual common species, resident species is down, which is kind of ... so, they got killed," Till­man concluded. "A lot of birds got killed."

Ken Zaslow, a retiree and regular CBC participant, chimed in, noting the delicate balance of plants, water, and wildlife that mesh together to create a healthy ecosystem. "If the trees are killed, say by salt water," he said, "that will affect birds that stop there on migration. Resident birds, they need a place, a habitat."

Tillman agreed: "I imagine some things are going to be favored and others, if the trees are destroyed, like your egrets need trees to have their nests, and if that's destroyed and they have to breed on the ground, then ..." She ladled some soup into her spoon and considered other effects of the storm, whether or not encroachment of saltwater in freshwater marshes would be a problem. "In the old days, you had places for them to move, but now ..."

"We're so built up," interrupted Jackie O'Keefe, a ponytailed native plant enthusiast. Tillman nodded. "We're so built up, you know, they don't have enough room to roam. It's not a very good future for birds and other wildlife, I don't think."

Consider the Warbler

The study of the delicate balance of all the components in an ecosystem and the ways that balance is mapped onto the climate and seasons is called phenology. It's an important part of what both Parmesan and La Sorte study, and it has been disrupted by climate change. Birds lay their eggs in spring, and they do so on a timeline evolved to have the most food available for their brood, be they bugs or seeds or whatever. Their food also operates on a seasonal timeline, hatching or producing seeds in the spring. But this timing is getting disrupted and the synchrony lost. Without a stabilized seasonal calendar ensuring the availability of resources necessary to successfully reproduce, birds and other wildlife populations are at risk.

Another change in the annual routine of birds is the shift in their range. Birds and wildlife in general are documented as moving poleward and upward (in elevation) in patterns corresponding to global warming.


These maps, from the Birds of North America as maintained by the Cornell Lab of Ornithology, detail the flight paths of three warblers seen in Austin during the Christmas Bird Count in December of 2017. The CBC takes place when the three species should be in their nonbreeding ranges, as noted in blue. For each bird, Austin is nowhere near those ranges. See more maps at www.birdsna.org.

"Individual birds are not saying to themselves, 'Oh gee, it's a little warmer, I can go a little further north than I usually go,'" Par­me­san said of this phenomenon. "They're going back to the same place they've always gone. It's the accident or maybe the occasional good weather spell that leads them to go somewhere new, and if it turns out that – as we've been getting climate change – that somewhere new is becoming more suitable, you've got the accidental pair that ends up further north, if they breed and that breeding is successful, then their offspring are trained in that new place, and they're more likely to go back to that spot a little further north. It's a slow process. So, to be finding, at this point, that about 50 percent of species have moved poleward, it's sort of a surprisingly high number."

The naturalists at the Bird Count were aware of the results of the research their data entry serves. They have observed the trends themselves over time, noting the increased presence of birds previously uncommon to the area, like the white-winged dove, which was historically more restricted in summer range to the Sonoran Desert, and the Eurasian collared dove, whose range has expanded from Florida to much of the contiguous United States. They have also noted the earlier arrival of other migratory birds, like the rare and endangered golden-cheeked warbler, whose breeding habitat is limited to within Texas. Both observations are in keeping with expectations of an overall warming climate, one that arrives at spring earlier and sustains warmer temperatures throughout the year.

Over a sandwich, Zaslow remarked, "The data shows that the range of birds has changed. Birds that normally wouldn't go north, their range is extending further north because of climate change. Also, bird migration – are birds migrating earlier or ...?"

"I think it's kind of hard to say," Tillman responded. "I know golden-cheeked warblers seem to be coming back earlier. Last year the Christmas Bird Counts were showing some birds are wintering further north, yeah, and of course we have a lot of birds that used to be South Texas birds and they're coming into Central Texas and they're here all the time, you know."

O'Keefe noted a change last fall. "We had great South Texas butterflies here! A lot of the plants are getting out of sync as well, in terms of blooming earlier and that, you know, those things don't coincide with their birds or their bugs, then you can have some real disjointedness."

"Yeah, and butterflies, they're noticing that they're coming out before their plants. So that's why you have to go out and enjoy what you're seeing," Tillman concluded. "Except for the grackles. It never occurred to me how many people think grackles are crows. They really look very different."

We finished the count that day on the land of a man Tillman only knows as "Christ­mas Bird Count Joe." He lets her observe the ponds on his land every year, as it falls within the boundaries of Tillman's usual area. We arrived there in the late afternoon, rain still dampening us and our equipment. We plodded around puddles and cow patties to peek into Joe's barn for any owls and set up a scope to tally the birds on the ponds. We entered our last tally for the day and left to join the other groups for a final count.

Poleward and Upward

A few weeks later the data compiler emailed me: "The total official number of countable species was 145. The Townsend's Warbler found by John Marsh during the count on the south shore of Lady Bird Lake was refound the next day. This is a very unusual bird for Travis Co at any time of year. While refinding the Townsend's, on the 17th, birders found, in the same location, a Cape May Warbler and a Chestnut Sided Warbler. All these birds should be in central or South America now."

What are the birds telling us?

It is unclear whether these wayward individuals spotted by CBC birders will pair up with a partner and serve as a pioneer of winter range expansion. They are, though, well outside of their regular range. The Townsend's warbler winters along the edge of the Pacific Coast and in Central America and Mexico. During its winter, it feeds almost exclusively on scaly insects' secretions, so an abrupt change in timing or winter range that disrupts the availability of such insects could present a problem for population survival. Similarly, the Cape May warbler spends its winter in the West Indies, where, with its uniquely adapted curled, semitubular tongue, it collects nectar. The Chestnut-sided warbler winters in moist tropical forests throughout Central America. While there would need to be more than individual sightings to mark a range shift – according to data entry, all of these sightings appear to be either the only or one of two recorded in Central Texas in the winter of 2017-2018 – with 50% of species expanding their ranges poleward and upward, they may well be harbingers of a forthcoming shift in range.

Like a Bird on the Wire

Dr. Parmesan notes some steps conservationists can take to help birds access the resources they need and mitigate the negative consequences of climate change. One important step is the protection and extension of habitats to "recover the corridors between habitats that we've taken away to allow that movement of species through the landscape, which is what climate change is driving them to do." Another is landscape management: the provision of native plants, of vegetation and lakes that create a cooler habitat. "There are a lot of things that conservation biologists can do even if you can't do anything about the amount of CO2 going in the air," she says.

Texas has witnessed some successful conservation programs, most notably championing the striking, formerly endangered brown pelican. In 1973 a census tabulated a paltry 12 breeding birds. That number has since risen to about 12,000, though undoubtedly Harvey has dented their population numbers. This resurgence is largely due to a concerted effort from Audubon Texas' Coastal Conservation program, who organize along some 600 miles of Gulf coastline.

Conservation efforts in Texas can be difficult, with the vast majority of the massive state – about 95% – privately owned. Shifts in population demographics and the parsing of private land into smaller pieces exacerbate the ability to effectively organize. Wildlife management associations are a type of co-op that allow landowners to come together and address habitat management, but they depend on a similarly minded effort from all participants. It may perhaps be easier to focus on maintaining the status of protected land and working within those habitats to make them as amenable as possible to the birds who populate the area, be they longtime residents and migrants or species newly expanded into the area.

Such efforts are going to become increasingly necessary as threats to wildlife arise from many directions and in increased severity. There are the more subtle disruptions of natural rhythms that limit their resources. There are also the catastrophic storms and events that do violent, immediate damage to populations. Loss of habitat like prairieland and nesting islands has been observed to dent population tallies. The rare golden-cheeked warbler depends heavily on the availability of the juniper trees in which they nest, and the loss of these trees has negatively affected their population numbers. Seasons of drought and destructive fires, not uncommon in Texas and both exacerbated by climate change, mean a loss of habitat and wildlife.

Ecologists fastidiously analyze citizen science-provided data to track and tally bird populations and examine the ways they respond to all of these threats. This research shows marked trends in behavioral responses. It also points to anthropogenic climate change as the impetus for these trends, leaving the concerned and conservation-minded wondering, beyond birds, how people will adjust their behavior in response to climate change.


This story has been updated to accurately reflect the flight paths of golden-cheeked warblers.

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