The Eastern Towhee, a bird of scrub and thickets, is a common resident in the southeast United States. One subspecies migrates north in summer.
They are a prime example of a species that is considered “Least Concern” by the International Union for Conservation of Nature (IUCN), but “High Risk” in National Audubon’s assessment of birds under climate change. In their 3.0 C scenario, they predict it would lose 83% of its current breeding range, while gaining only 23%.
These projections are consistent with recent literature showing poleward shifts of species ranges– of the northern edge of their range, of the southern edge, and of their range’s geographic center. The predictions for Eastern Towhee are among the most dramatic.
Recent research also suggests that non-migratory and short-distance migrants are more adaptable to climate change than are long-distance migrants, and more able to shift their ranges. Indeed, we are already seeing that with Eastern Towhee. The Audubon projections appear to be in progress.
Based on Breeding Bird Survey (BBS) data, the Eastern Towhee breeding population in Florida has declined over 50% since the late 1990s. The timing of this is consistent with worldwide ecological shifts which began in the mid-1980s.
The white-eyed subspecies appears to be already in trouble. eBirders in Florida in May and June are encountering the species half as often as they were just six years earlier.
Not all range shifts are due to climate. As a scrub specialist, the Eastern Towhee prefers habitat that is in the act of regrowth, such as after a fire or being cleared. But they don’t want a forest either. To quote the Birds of the World species account for Eastern Towhee: “As farmland is abandoned, successional changes produce suitable midseral habitats that towhees favor, and their numbers increase. But, successional time is against towhees, and their numbers decrease as seres age.” That may be the explanation for the Georgia data (orange dots), which show a decline in the late 60s and early 70s, possibly due to forest growth or land clearance for development, and then a leveling off.
As the climate warms, many species are expanding north and/or declining in the southern part of their range. But these need not happen simultaneously. Opportunities for suitable habitat may open doors in the north, and doors may close in the south, at different times. There is evidence of Eastern Towhee expansion in Minnesota, but look at the vertical axis; it does not compare with the losses in Florida.
In Florida, the white-eyed subspecies faces extinction based on National Audubon’s 1.5C scenario. They appear to have declined dramatically in the past two decades.
A number of recent academic papers have described northward shifts of bird species in both North America and Europe, driven by climate change. These papers usually present aggregated results from dozens of species; they rarely provide details for any specific species. These maps are intended to offer that.
While there are tremendous species-specific differences, non-migratory resident birds (such as Northern Cardinal, Carolina Wren, Tufted Titmouse, and Red-bellied Woodpecker) appear to be the most adaptable and have expanded their ranges the most. This seems to be primarily driven by warmer winters and, for some species, is further augmented by bird feeders.
I created these maps using eBird, so the usual caveats apply– they don’t necessarily include all records (though many historical out-of-range records are indeed included), and eBird reporting, which became widespread only after 2010, continues to increase dramatically each year. To draw the lines, my intent was to capture the primary range area — and more — but I deliberately excluded the furthest ten to fifteen outliers for each line.
Two of the academic papers that report climate-driven range expansions in eastern North America are listed below, along with their abstracts.
Prince, K. and B. Zuckerberg. 2016. Climate change in our backyards: the reshuffling of North America’s winter bird communities. Global Change Biology 21(2): 572-585.
Much of the recent changes in North American climate have occurred during the winter months, and as result, overwintering birds represent important sentinels of anthropogenic climate change. While there is mounting evidence that bird populations are responding to a warming climate (e.g., poleward shifts) questions remain as to whether these species-specific responses are resulting in community-wide changes. Here, we test the hypothesis that a changing winter climate should favor the formation of winter bird communities dominated by warm-adapted species. To do this, we quantified changes in community composition using a functional index–the Community Temperature Index (CTI)–which measures the balance between low- and high-temperature dwelling species in a community. Using data from Project FeederWatch, an international citizen science program, we quantified spatiotemporal changes in winter bird communities (n = 38 bird species) across eastern North America and tested the influence of changes in winter minimum temperature over a 22-year period. We implemented a jackknife analysis to identify those species most influential in driving changes at the community level and the population dynamics (e.g., extinction or colonization) responsible for these community changes. Since 1990, we found that the winter bird community structure has changed with communities increasingly composed of warm-adapted species. This reshuffling of winter bird communities was strongest in southerly latitudes and driven primarily by local increases in abundance and regional patterns of colonization by southerly birds. CTI tracked patterns of changing winter temperature at different temporal scales ranging from 1 to 35 years. We conclude that a shifting winter climate has provided an opportunity for smaller, southerly distributed species to colonize new regions and promote the formation of unique winter bird assemblages throughout eastern North America.
Saunders et al. 2022. Unraveling a century of global change impacts on winter bird distributions in the eastern United States. Global Change Biology
One of the most pressing questions in ecology and conservation centers on disentangling the relative impacts of concurrent global change drivers, climate and land-use/land-cover (LULC), on biodiversity. Yet studies that evaluate the effects of both drivers on species’ winter distributions remain scarce, hampering our ability to develop full-annual-cycle conservation strategies. Additionally, understanding how groups of species differentially respond to climate versus LULC change is vital for efforts to enhance bird community resilience to future environmental change. We analyzed long-term changes in winter occurrence of 89 species across nine bird groups over a 90-year period within the eastern United States using Audubon Christmas Bird Count (CBC) data. We estimated variation in occurrence probability of each group as a function of spatial and temporal variation in winter climate (minimum temperature, cumulative precipitation) and LULC (proportion of group-specific and anthropogenic habitats within CBC circle). We reveal that spatial variation in bird occurrence probability was consistently explained by climate across all nine species groups. Conversely, LULC change explained more than twice the temporal variation (i.e., decadal changes) in bird occurrence probability than climate change on average across groups. This pattern was largely driven by habitat-constrained species (e.g., grassland birds, waterbirds), whereas decadal changes in occurrence probabilities of habitat-unconstrained species (e.g., forest passerines, mixed habitat birds) were equally explained by both climate and LULC changes over the last century. We conclude that climate has generally governed the winter occurrence of avifauna in space and time, while LULC change has played a pivotal role in driving distributional dynamics of species with limited and declining habitat availability. 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.
Like so many species, the Carolina Wren is expanding northward. And, like many of those species, this expansion started decades ago, before any measurable climate change, but has exploded in the past decades with climate change.
The Carolina Wren has been expanding north since the 1800s due to habitat recovery after deforestation (Haggerty and Morton, 2020 – the Birds of North America (BNA) species account). What makes the recent Carolina Wren data so interesting is that we can clearly see, in its expansion into Canada, its battle with winter weather conditions.
The species is known for “decimation… by severe winter conditions” (BNA) at the northern limits of its range. The same account notes that “severe winters have apparently been infrequent enough during the 20th century to allow populations to expand and move northward.” Indeed, one of the key conclusions of an analysis of climate change in southern Ontario was that there has been “a decrease in the frequency of cold temperature extremes”. While the wren is aided against cold snaps by bird feeders, the climate trend, at least in Canada, is in its favor. The report noted an overall average increase of 1.5C.
As the wren expanded, certain record-breaking and persistent cold waves knocked the population back, where it restarted. It’s also clear that it is restarting from a higher position each time, thus building its numbers and continuing its expansion.
The cold snaps denoted on the graph were particularly severe in southern Ontario. A more detailed look at weather data may reveal a more complicated pattern and even greater correlation to warmer winters.
This blog post is merely to provide a visual illustration, by way of a map, of the expansion of the California Scrub-Jay across Washington, British Columbia, eastern Oregon, Idaho, and even Montana (one record so far). It is intended to complement my more detailed article, “Tracking Expansion of the California Scrub-Jay Into the Pacific Northwest”, in the Washington Ornithological Society (WOS) News, August-September 2021 edition.
As becomes clear in the article, these are not hard lines. The jays are advancing gradually, not in a solid wave. Typically, a single jay will appear well outside the known range (e.g. Spokane). Within a year or two, there will be several. Then they’ll be breeding. Then they will begin expanding further. Meanwhile, a wave of jays will be backfilling the new territory, with densities increasing annually. The lines in this map are as much art as science, but are intended to show the primary region were jays were “regular and expected”. There were always outliers, pioneer dispersers expanding the range. Records beyond the 2020 line are shown as pale blue dots.
The jay’s expansion, when considered in the context of timing and trends in other species, is likely a function of a warming climate combined with suitable food sources. For more discussion of this, see the WOS article linked above.
It will be interesting to see where the 2030 scrub-jay “contour line” will be. I predict they’ll be on Vancouver Island from Victoria to Campbell River, as well as up the Sunshine Coast, up the Okanagan Valley to Kelowna and possibly Kamloops, and east to Idaho, from Coeur d’Alene in the north throughout the Snake River Valley in the south.
After that, they face some formidable hurdles. The biggest obstacles to their expansion further north and east will be habitat with limited food sources (e.g. high mountains). That said, they’ve already shown some ability to travel up mountain valleys and potentially cross the Cascades north of Mount Rainier.
In a very frank and data-rich webinar, fire ecologist Hugh Safford (USDA Forest Service and research faculty at Department of Environmental Science and Policy at UC Davis) offers “Some ruminations on fire and vegetation trends in California”. He explains the causes of the dramatic increase in megafires and what can be done about it.
The webinar was co-sponsored by the Yolo Interfaith Alliance for Climate Justice and Cool Davis and presented on May 5, 2021.
Safford’s presentation starts at 13:23 of the video. The equally enlightening Q&A session begins at 48:20.
Here is a summary of some of the key points:
The annual burned area has been rising rapidly since the 1980s, almost entirely in northern California.
This is largely due to fire exclusion caused by the removal of Native Americans as land managers and increased drought and record vegetation dryness caused by climate change.
Since 1999, burning over a million acres/yr now occurs regularly; this had not happened before 1999.
Pre-EAS (Euro-American Settlement) burning by Native Americans totaled up to FOUR million acres/year (but these were low severity fires that primarily burned the understory and smaller trees).
“Euro-Americans, when they showed up in the 1850s, and for that matter today, had no idea how important fire was to the functioning of these ecosystems and they feared it and felt like it was something they needed to stop. After a hundred years of that, it’s really biting us in the butt now because now we have jungles of fuels, we’ve cut most of the big fire-resilient trees out of the system, and when we get the ignitions start we can’t stop the fires anymore. Until about the 1990s, it was easy to put fires out in the forests.”
Pre-EAS forests were at least 40% old growth; current forests are only 6% old growth and highly vulnerable to high severity fires, as they are 4-5x denser than pre-EAS.
“Every single fire projection we found in the literature predicts bigger fires, more fires, and more severe fires, basically until we’ve burned so much of California that there actually isn’t much woody vegetation left to burn.”
Expect the loss of conifers and an increase in non-native grassland.
Changes already underway: loss of blue oak woodland, ponderosa, yellow pine, and subalpine pine; increase in hardwoods. Loss of sage scrub and chaparral in southern California. Many burned areas are quickly invaded by non-native grasses and will not recover. Incense cedar and white fir may become more dominant trees in California forests.
Fires in the Coast Range are now destroying chamise and blue oaks with limited evidence of re-sprouting.
In the short run, there’s not a lot we can do to manage climate, but there’s a lot we can do to manage fuels.
There’s been a huge renaissance, especially among Native tribes, to use controlled burns to manage forests. California’s new fire resilience plan supports the use of controlled burns. Northern Australia has had great success allowing Aboriginies to manage forests. Opportunities are limited, however, because of development.
The combination of drought cause megafires in the Sierra to produce “Hiroshima-type landscapes”, burning old growth.
How to stop fires: Forest thinning is critical, but it’s not economical to harvest small trees, so the government will have to subsidize it. For example, we can use the cut trees for biomass energy, as it done in Scandinavia. This is the only way to save large old growth trees and healthy forests. “We have to cut a lot of trees. We don’t have a choice…. We can create forests that can handle large fires, or we can sit around and watch it all vaporize.”
There are a lot of reasons why I’m moving from California to Washington, including family and other personal considerations. But one reason, one big reason, is California’s rapidly changing climate.
It was late February in the Coast Range of northern California when I was wearing shorts and a t-shirt. Dust swirled around my car in the dirt parking lot at Cold Canyon. The car thermometer, warmed by a sun that felt imported from Palm Springs, said 87 degrees; it was actually only 77. A hint of ash, omnipresent since The Fire last summer, remained in the air.
The hillsides were green with the new growth of non-native grass, which was responding to a recent heavy rain. That was deceptive. More than half the rain we’d had in the previous eight months came in that single event. We had six inches of rain in all of 2020. Looking beyond the grass, nearly every tree – blue oaks and gray pines – on the hillsides was dead, burnt black and orange monuments to a previous era. For our local blue oak woodland, that era ended last year and, given that recruitment of saplings is unlikely due to heat, fire, and cattle, it was an era that will never return.
Massive die-offs are eliminating blue oaks from the southern third of their range. Black oaks are marching up the Sierra, displacing Ponderosa pine, which are marching up, displacing firs. Everyone is on the move. Oak woodlands are becoming oak savannahs, oak savannahs are becoming grasslands, grasslands are becoming rocky high deserts. Arizonification is happening quickly, thru heat, drought, and ultimately, thru fire.
Virtually all of the east slopes of the Coast Range between San Francisco Bay and the Trinity Alps has burned in the past ten years. In the Sierra, one can practically predict where the next fire catastrophe will happen, because it hasn’t burned yet (hint: Lake Almanor, Placerville, Arnold).
It was a beautiful day—for April. But February has become April, April has become May, and June, July, August, September, and even October and November have become unrecognizable. Every year more heat records are broken. Hottest summer, hottest month, most days over 100, most days over 90. The list goes on, each year breaking the records set the previous year. Weather data is normally highly variable; now it is a straight line—warmer and warmer. And smokier.
My cape honeysuckle and bougainvillea, both planted with a degree of optimism outside their recommended zone, used to die back so badly in the winter that each spring I was tempted to declare them dead and pull them out. Now they bloom year-round, looking like they’re in a courtyard at a hotel in the tropics. We haven’t had a real freeze in seven winters.
The songs of lesser goldfinches on my street are a depressing warning. I can’t take two steps outside without seeing or hearing a bird that reminds me that our climate has seriously changed. Western tanagers, house wrens, and turkey vultures are regular in winter now. The lesser goldfinches have come out of the arid hills and are quickly becoming one of the most ubiquitous nesting birds in Davis. (I know this definitively because one included an imitation of a canyon wren in its song.) What’s more, at least four Say’s phoebes, essentially a high desert species, are scouting for nests in town now. A fifth arrived on my block last week, singing as if on territory. They’ve been doing this for a few years and their numbers are growing.
I’m leaving. I’ve lived in California fifty-five years but it’s no longer the state I grew up in.
We’re headed to the Olympic Peninsula in Washington. We are fortunate to be able to do so.
I feel like a frog in a boiling pot. I’m getting out. I’m saying goodbye to California, but I feel it has left all of us without saying goodbye to anyone.
I do believe that Homo sapiens may ultimately win the climate battle and bring atmospheric CO2 back down to 300 ppm or something. But that’s a hundred years off. And there’s no guarantee we can stop the tide of Greenland and Antarctic ice melt to prevent sea level rise. In the meantime, in the next 50 to 100 years, it’s going to get a lot warmer. And we may ultimately lose New York City, Singapore, Mumbai, and every other low-lying coastal city. My new home is fifty feet above sea level. Well, probably forty-nine and a half now.
As the climate warms, different thresholds are crossed for different species at different times. For the Lesser Goldfinch, that time seems to be now—both in the core and northern edges of its range, where the species is increasing, and in some parts of the southern arid regions, where it is decreasing.
As I prepare to migrate myself from Davis, California to Port Townsend, Washington, I’m serenaded by Lesser Goldfinches every time I step outside. This is a new thing, a warning of coming heat and smoke brought by a beautiful voice. A more open and arid country version of the American Goldfinch, until five or ten years ago, Lesser Goldfinches were sparse breeders in Davis. I would get a few of them mixed with Americans at my feeder in winter, but I’d have to go west to the more arid edges of the Sacramento Valley, or up into the hot dry foothills, to find them in the breeding season.
They arrived in my neighborhood as nesters about five years ago. This year, 2021, they seem to be the most ubiquitous singing bird, setting up terrorities throughout the town. Friends in Sacramento have reported the same. This comes after several years of record heat and lack of rain (only 6″ in all of 2020).
Here’s what the eBird data says. For comparison, Northern Mockingbird, one of the most common birds in town, is reported from about 20 eBird locations in Davis each June (ranging from 16 in 2015 and 14 in 2016 to 18-22 in the more recent years as eBird users and reports increased). Using mockingbird as a metric for Davis, it’d be fair to say that 20 sites represents close to 100% presence throughout the town, and that number was probably 25% lower (i.e. 15 sites) in 2015. Lesser Goldfinches have increased from reports from four sites in June of 2015 (representing about 20% of the town) to 17 sites in June of 2020 (representing 85% of the town). It feels like it will be 100% this year.
They are not the only arid-country species increasing in Davis as a breeder. Nesting Say’s Phoebes have expanded up from the south, with multiple pairs in Woodland each year (and it’s looking like Davis this year as well).
As with so many less-migratory species, Lesser Goldfinches are expanding north into the Pacific Northwest and beyond. Their colonization of the Columbia River Valley began in the 1950s, with the first state of Washington record in 1951; they are now established around Portland, The Dalles, and in the vicinity of Clarkston on the Idaho border. They remain rare elsewhere, but increases in records have been dramatic in recent years. In the northern Puget Trough region (Chehalis north thru Puget Sound to Canada), June records have increased from 1 in 2015 and 2016 to 10 in 2020 (as reported on eBird). While they have clearly gained a toe-hold in Olympia and Puyallup in the South Sound region, in 2020 they made appearances in Victoria and Vancouver, Canada (not shown in the data because these records were in May, not June).
This is a pattern seen in other resident and less-migratory species. Many of those that were already growing before detectable climate change (around 1985) have expanded noticeably since then. Anna’s Hummingbird is the most dramatic example.
Further east, Lesser Goldfinches are moving due north from Yakima and Kennewick into the Okanagan Valley. June records in this region have increased from zero in 2015 to eight in 2020.
In the Mojave Desert, Lesser Goldfinches have declined. Iknayan and Beissinger (2018) reported them from only 43% of 61 study sites, compared to 68% historically. This is part of a massive avian community collapse in the Mojave Desert, as extreme aridity is pushing many species beyond their limits.
Renewable diesel already accounts for 20% of California’s diesel supply and is projected to grow well beyond 50% by 2024, expanding to include jet fuel, where it is called “sustainable jet fuel”. Renewable propane is also produced during the refining process. Renewable gasoline, unfortunately, is still not economically feasible.
Increasingly, refineries in California are ramping up to produce RD from local feedstock. Two of the state’s largest refineries, Phillips 66 and Marathon in the Bay Area, are currently closed, using the Covid downturn to retrofit their operations into making RD. They will each produce 20% of the state’s diesel in the form of RD; they will completely cease using crude oil as an input. Other smaller refinery conversions are underway in southern California.
At the state level, California’s ever-lowering cap of tradeable permits under the AB32 cap-and-trade program is finally biting hard enough to change incentives. Carbon credits are now yielding about 30 cents/gallon and is likely to rise. Because this comes from traded permits, it is not a direct payment from government funds.
Combining federal and state incentives, a refinery converting from conventional to renewable diesel reaps an additional $1.30/gallon. If the Phillips 66 project goes to its full 800 million gallons/year, that’s at least a billion dollars each year in subsidies – from tax credits and tradable carbon credit sales.
California has already reduced greenhouse gas emissions 15-20% since the peak in 2004. This has been achieved during a period of significant economic and population growth; emissions per gross domestic product are down about 45%. Because the transportation sector has been among the most challenging for reducing emissions, the RD revolution will go a long way to helping California reach net zero by 2050. The Biden Administration is using California’s carbon reduction measures as a model for the nation.
Two recent papers concluded that many breeding bird species in southern California and Nevada deserts have declined dramatically due to climate change.
In their abstract, Iknayan and Beissinger (2018) summarized, “We evaluated how desert birds have responded to climate and habitat change by resurveying historic sites throughout the Mojave Desert that were originally surveyed for avian diversity during the early 20th century by Joseph Grinnell and colleagues. We found strong evidence of an avian community in collapse.”
Of 135 species assessed (which included some wintering and migrating species, as well as breeding species), 39 had significantly declined; only one (Common Raven) had increased. This was in stark contrast to similar assessments they conducted of Sierra and Central Valley sites, where more species had increased than decreased and there were no overall declines (not to say there weren’t winners, losers, and range shifts within those regions).
Detailed analyses suggested less rainfall and less access to water was the primary driver. Habitat change only affected 15% of the study sites and was of secondary importance. They found no evidence of expansion of species from the hotter, drier Sonoran Desert (e.g. Phainopepla, Verdin, Black-throated Sparrow) into the Mojave Desert.
Consistent with a community collapse, declines were greatest among species at the top of food chain — carnivores such as Prairie Falcon, American Kestrel, and Turkey Vulture. Insectivores were the next most impacted, and herbivores the least. But the declines affected both common and rare species, both generalists and specialists.
A follow-up study by Riddell et al (2020), also involving Iknayan and Beissinger, focused on the thermoregulatory costs — the water requirements to keep cool — for the declining species. They found that “species’ declines were positively associated with climate-driven increases in water requirements for evaporative cooling and exacerbated by large body size, especially for species with animal-based diets.” Larger species get much of their water from the insects they eat. They estimated larger species would have to double or triple their insect intake to meet their water needs, though insect abundance is lowest July thru September.
Iknayan and Beissinger conclude, “Our results provide evidence that bird communities in the Mojave Desert have collapsed to a new, lower baseline. Declines could accelerate with future climate change, as this region is predicted to become drier and hotter by the end of the century.”