Heading south for winter, more birds are choosing the Pacific Northwest

Many papers predict that bird ranges will shift northward with a warming climate (Wu et al 2018, Langham et al 2015).

Many studies have already documented that this is happening (Illán et al. 2014, Virkkala, R. and A. Lehikoinen 2014, Hitch and Leberg 2007, and La Sorte and Thompson 2007).

And some have documented poleward range shifts specifically for wintering ranges (Saunders et al 2022, Hampton 2019, Paprocki et al 2017, Prince and  Zuckerberg 2016, and Paprocki et al 2014).

I’ve previously written about an increase in insectivore bird species in winter associated with a warming climate in the Sacramento Valley. As the Putah Creek Christmas Bird Count (CBC) compiler, it was hard not to notice the trends. Cassin’s Vireo, Black-throated Gray and Townsend’s Warblers, and Western Tanagers were becoming more expected in winter. We had crossed a threshold; we didn’t get freezes anymore. My bougainvillea and cape honeysuckle, which previously clung to life in winter, were now growing and blooming year-round. Fruit and insects were available to these birds.

Now in Port Townsend, Washington, we set a local CBC record for Yellow-rumped Warblers last year. This caused me to take a closer look at the data, focusing on Passerines that are rare or uncommon, and at the northern edge of their wintering range. They are: Hermit Thrush, Cedar Waxwing, Lincoln’s Sparrow, White-crowned Sparrow, Orange-crowned Warbler, and Yellow-rumped Warbler. For each of these, the PNW is at the northern limits of their wintering range.

I looked at their numbers and trends on the Portland, Olympia, Seattle, Bellingham, and Vancouver BC CBCs since the 76th CBC (winter 1975-76). I’ve got more notes on my methodology at the end.

Results

All have increased since 1975, generally with the uptick beginning in the 1990s. Here are the results of my inquiry.

The range maps are from eBird’s Abundance Maps. Red=summer; blue=winter; purple=year-round; yellow=migration. The graphs show the birds per party hour across the five CBCs, taking the total number of birds and dividing by the total number of hours across all five counts.

Hermit Thrush

Hermit Thrush has been increasing at a rate of 4.2% per year across all the CBCs. It has been increasing across all five of the counts, most strongly in Vancouver (4.1% annual growth) and most tepid in Seattle (0.6%). The overall average   It is most common on the Portland count, which has averaged 26 Hermit Thrushes per count since 2009.

Cedar Waxwing

Of the six species I focused on, Cedar Waxwing showed some of the most erratic growth, averaging only 2.5% per year. That said, it has been above average 8 of the last 9 years. To illustrate the unpredictable nature of waxwings, they have actually been declining on the Olympia (-2.3%/yr) and Vancouver (-4.1%/yr) counts. They are increasing the most on the Portland count (3.0%/yr).

Lincoln’s Sparrow

Lincoln’s Sparrow has been increasing steadily, from near zero, at an overall rate of 3.6% per year. To put this in perspective, these five CBCs tallied 5 or fewer individuals, summed across all counts, in each of the first five years of this analysis. In each of the last five years, these counts, in aggregate, tallied between 34 and 52 individuals. Growth has been strongest on the Olympia count (4.6%/yr) and weakest on the Bellingham count (1.7%/yr).

White-crowned Sparrow

Despite the eBird map, White-crowned Sparrow is a regular overwintering species in the PNW. The five counts, in aggregate, tally between 100 and 750 individuals each year. They’ve been increasing at a rate of 1.8% per year, strongest in Seattle (3.1%/yr) and weakest in Vancouver (-2.5%/yr, the only count with declining numbers).

Orange-crowned Warbler

Orange-crowned Warbler has seen dramatic increases, averaging 5.0% per year, highest in Olympia (7.2%/yr) and lowest in Bellingham (3.2%/yr). The numbers, however, are still small. Aggregate numbers across all counts were zero five of the first eleven years of this analysis (easily seen on the graph). Double digits were not reached until 1999. The last ten years, however, have averaged 15 individuals across all the counts, making this an expected species in winter now.  

Yellow-rumped Warbler

Yellow-rumped Warbler wins the award for poster child of species increasing in winter at the northern edge of their wintering range. They’ve been increasing at a rate of 5.3% per year. Interestingly, this growth is concentrated in the south. Portland (3.7%/yr), Olympia (3.4%/yr), and Seattle (6.1%/yr) have seen the most growth, while Bellingham (-0.5%) and Vancouver (-5.0%) have seen declines. Perhaps those Fraser River winds are too cold for warblers. 

Methodology

The data includes bird per party hour for the Portland, Olympia, Seattle, Bellingham, and Vancouver BC Christmas Bird Counts from the 75th count (winter 1975-76) to the 120th count (winter 2019-20). The 121st count was impacted by the pandemic.

CBC (and Breeding Bird Survey) data is uniquely advantageous for looking at long-term trends such as climate change, as they both go back many decades with generally similar effort over time (for certain well-established counts). Nevertheless, there were some issues with this data:

  • I did not use the Portland data from the 76th thru the 82nd count, due to aberrantly low party hours relative to later counts.
  • The following data was missing entirely from the Audubon CBC database: Olympia 76th, 77th, 78th, 84th, 104th, and 110th counts; and Seattle 91st count.
  • The following counts had no (or obviously incorrect) data for party hours: Portland 104th count; Bellingham 111th, 112th, and 119th counts. Because they did have bird numbers, I approximated the party hours based on their counts in nearby years. I used 230 party hours for the Portland count and 200 party hours for the Bellingham counts.

Other climate-related bird changes in the Pacific Northwest

I’ve previously blogged about climate change and birds in the Pacific Northwest:

The invasion of the Pacific Northwest: California’s birds expand north with warmer winters looks at northward range expansions of Great Egret, Turkey Vulture, Red-shouldered Hawk, Anna’s Hummingbird, Black Phoebe, Townsend’s Warbler, and California Scrub-Jay, with some discussion of others as well. Note that Townsend’s Warbler, as a migrant that winters rarely in the PNW, fits with the group of birds described in this post.

The song of the Lesser Goldfinch: Another harbinger of a warming climate looks at increasing records in the PNW in summer.

Mapping the expansion of the California Scrub-Jay into the Pacific Northwest looks at the steady range expansion of this non-migratory species.

References

Hampton, S. 2019. Avian responses to rapid climate change: Examples from the Putah Creek Christmas Bird Count. Central Valley Birds 22(4): 77-89.

Hitch and Leberg. 2007. Breeding distributions of North American bird species moving north as a result of climate change. Conservation Biology 21(2): 534-9.

Illán et al. 2014. Precipitation and winter temperature predict long-term range-scale abundance changes in Western North American birds. Global Change Biology, 20 (11), 3351–3364.

Langham et al 2015. Conservation status of North American birds in the face of future climate change. PLoS ONE 10(9): e0135350.

La Sorte, F.A., and F.R. Thompson III. 2007. Poleward shifts in winter ranges of North American birds. Ecology 88(7):1803–1812.

Paprocki et al. 2014. Regional Distribution Shifts Help Explain Local Changes in Wintering Raptor Abundance: Implications for Interpreting Population Trends. PLoS ONE 9(1): e86814.

Paprocki et al. 2017. Combining migration and wintering counts to enhance understanding of population change in a generalist raptor species, the North American Red-tailed Hawk. The Condor, 119 (1): 98–107.

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.

Saunders et al. 2022. Unraveling a century of global change impacts on winter bird distributions in the eastern United States. Global Change Biology

Virkkala, R. and A. Lehikoinen 2014. Patterns of climate-induced density shifts of species: poleward shifts faster in northern boreal birds than in southern birds. Global Change Biology 20: 2995–3003.

Wu et al. 2018. Projected avifaunal responses to climate change across the U.S. National Park System. PLOS ONE 13(3): e0190557.

I try to maintain an updated list of references at the Birds and Climate Change Facebook group. At that page, click on Files to find the list.

Carolina Wren + Climate Change vs the Polar Vortex

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.

This phenomenon is most obvious – and even dramatic – among non-migratory species and short-distance migrants. The same thing is happening in the West (e.g. Anna’s Hummingbird, Turkey Vulture, Red-shouldered Hawk, Great Egret, California Scrub-Jay, Black Phoebe, Townsend’s Warbler, and others).

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 raw number of Carolina Wrens reported on Christmas Bird Counts in Canada. Over 95% of these come from southern Ontario. The cold waves marked on the graph were particularly record-breaking and long-lasting.

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.

eBird abundance map. The Carolina Wren has primarily been a species of edge habitat associated with moist southern forests.

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.

Predicted range changes for Carolina Wren by National Audubon under 1.5C scenario. This map is fairly accurate as the bird continues to colonize the St. Lawrence River corridor.
eBird map for December 2021 showing colonization from Toronto to Ottawa and Montreal and nearly to Quebec City.
A Carolina Wren fluffed up against the cold. Pic from National Audubon website.

Bird names matter: Top ornithologists and organizations endorse name changes for all species named after people

At the American Ornithological Society (AOS) Congress on English Bird Names on April 16, 2021, a host of prominent organizations and individuals endorsed “bird names for birds”, a widespread effort to rename eponymous or honorific species names with more descriptive names, focusing on their physical or ecological attributes. For example, Wilson’s Warbler could become Black-capped Warbler, Townsend’s Solitaire might become Northern or Juniper Solitaire, and Kittlitz’s Murrelet would probably be re-named Glacier Murrelet.

MacGillivray’s Warbler was named by John James Audubon after his friend, William MacGillivray, a Scottish ornithologist who never came to America. Audubon also coined its Latin specific, tolmiei, to honor William Fraser Tolmie, a Scottish employee of Hudson’s Bay Company based at Fort Nisqually during the period of Native removal. Scientific, or Latin names, are subject to international rules and are not the focus of this process.

While specific new names have not yet been chosen, representatives of the American Birding Association (ABA), National Audubon Society, as well as David Sibley and Kenn Kaufmann, all heartily endorsed developing a process to make the changes, noting that new names would engage a larger audience, contribute to greater equity and inclusivity among birders and the interested public, and could aid in public communication and conservation efforts.

The effort has grown out of the national reckoning on racial equality in the aftermath of the George Floyd killing. Movements to change names are underway with regard to parks, mountains, streets, other wildlife, and even rock-climbing routes. Current names generally go back to the eighteenth and nineteenth centuries during European expansion across North America and recall an era of conquest, when species and landforms were “discovered” – and some named after the individual who documented them, or after their friends and colleagues.

An FAQ, full list of the panelists, and a video of the Congress can be found at the AOS English Bird Names website. The direct link to the video is here.

Sibley commented that, the more he learns about the names, “the more they cast a shadow over the bird” and “the name doesn’t mean just the bird anymore. They have baggage.” Out of respect for people and the birds, they “should not have to carry a reminder of our own fraught history.” Choosing between stability and respect, Sibley stated “I choose respect.”

Name changes over social justice concerns began last year when McCown’s Longpsur was changed to Thick-billed Longspur, after widespread outcry because McCown was a Confederate general and involved in the ethnic cleansing of Native Americans. A proposal in 2018 for that name change was roundly rejected. 

Name changes for these reasons are not new; most birders can probably recall the switch from Oldsquaw to Long-tailed Duck in 2000. At that time, the American Ornithologists’ Union, the precursor to the AOS, asserted that the name change was not for reasons of “political correctness” but merely to conform with usage elsewhere.

The Bird Names for Birds website includes bios of various people memorialized with bird names. For example, Townsend (of the solitaire, warbler, and storm-pretrel) collected Native skulls for his friend Samuel Morton, author of Crania Americana. The November 2020 issue of Birding magazine focused on name changes, with a strong endorsement by ABA President Jeffrey Gordon and a longer article providing historical background. It is available here for ABA members.

Bird Names for Birds, a group of interested birders, was instrumental in reaching out to the larger organizations to participate in the congress. In their words, “Eponyms (a person after whom a discovery, invention, place, etc., is named or thought to be named) and honorific common bird names (a name given to something in honor of a person) are problematic because they perpetuate colonialism and the racism associated with it. The names that these birds currently have—for example, Bachman’s Sparrow—represent and remember people (mainly white men) who often have objectively horrible pasts and do not uphold the morals and standards the bird community should memorialize.” They describe such names as “verbal statues” that should be removed.

Jordan Rutter of Bird Names for Birds argued that, when reaching out to the public to protect an endangered sparrow, Bachman’s Sparrow has much less appeal than an alternative name rooted in local ecology that the public could identify with. Kaufmann pointed out that Bachmann was a pro-slavery white supremacist and that the species was formerly known as the Pinewoods Sparrow.

In the AOS’s own language, “The Community Congress opens the discussion on the complex issues around eponymous English Bird Names…. The specific aim of the Community Congress is to provide an opportunity for a broad range of stakeholders from the birding and ornithological community to share their viewpoints, including challenges and opportunities from their perspectives, to best inform future next steps to address the issue of naming birds after people.”

The AOS Congress on English Bird Names was superbly moderated by José González, providing a model for the process ahead.

Keepers of various ornithological databases also participated in the Congress, including representatives for eBird, Christmas Bird Counts, Breeding Bird Surveys, and the Bird Banding Laboratory. While noting potential complications with name changes (and changes in four-letter banding codes), they all agreed the hurdles were not insurmountable. Indeed, name changes, as well as taxonomic lumps and splits, occur every year, with name changes being the simplest of the three to address in data management. eBird currently supports bird names in 47 languages, including 14 different versions of English. Where Americans see Black-bellied Plover, Brits see Grey Plover.

Marshall Iliff of eBird pointed out that the effort is also an opportunity to clean up old taxonomic messes, pointing out that Audubon’s Shearwater has been used for eleven different combinations of nine different taxa. In this case, he said, fresh names for specific taxa will provide clarity, not confusion. He embraced a worldwide effort to “dig into the essence of each species” to “find inspired and appropriate names.”

For now, the effort will be limited to primary eponymous English bird names. The effort will not include secondary names (e.g., American Crow, named after the continent, which was named after Amerigo Vespucci). Other problematic names, such as Flesh-footed Shearwater for a bird with pink feet, were not discussed.

Many suggested using Native names for species, though most stated this could be challenging because 1) names from Native languages may have been lost, or 2) most bird species’ ranges span multiple historic aboriginal territories and languages, creating a conundrum over which indigenous word to use. The exception to this is Hawaii, where indigenous names are already in widespread use. Among mammals, moose, raccoon, and skunk are all derived from Algonquian.

Does Lawrence’s Goldfinch deserve a better name?

Looking at Version 8.0.8 (March 12, 2021) of the ABA Checklist, 115 of the 1,123 species, or a little over 10%, are named after people. Of these, 2 (Bishop’s Oo and Bachman’s Warbler) are considered extinct, and 20 others are Code 4 or 5, meaning they occur extremely rarely in the ABA area (though three of these are regular in Mexico, within the AOS area). The remaining 93 are all Code 1, 2, or 3, and can be expected to be seen in the ABA area regularly.

Here are the 113 non-extinct species from the ABA Checklist.

Ross’s Goose

Steller’s Eider

Stejneger’s Scoter

Barrow’s Goldeneye

Gambel’s Quail

Erckel’s Francolin

Clark’s Grebe

Vaux’s Swift

Rivoli’s Hummingbird

Anna’s Hummingbird

Costa’s Hummingbird

Allen’s Hummingbird

Xantus’s Hummingbird

Ridgway’s Rail

Wilson’s Plover

Temminck’s Stint

Baird’s Sandpiper

Wilson’s Snipe

Wilson’s Phalarope

Kittlitz’s Murrelet

Scripps’s Murrelet

Craveri’s Murrelet

Cassin’s Auklet

Sabine’s Gull

Bonaparte’s Gull

Ross’s Gull

Franklin’s Gull

Pallas’s Gull

Belcher’s Gull

Heermann’s Gull

Forster’s Tern

Salvin’s Albatross

Wilson’s Storm-Petrel

Swinhoe’s Storm-Petrel

Leach’s Storm-Petrel

Townsend’s Storm-Petrel

Tristram’s Storm-Petrel

Murphy’s Petrel

Fea’s Petrel

Zino’s Petrel

Cook’s Petrel

Stejneger’s Petrel

Bulwer’s Petrel

Jouanin’s Petrel

Parkinson’s Petrel

Cory’s Shearwater

Buller’s Shearwater

Newell’s Shearwater

Bryan’s Shearwater

Audubon’s Shearwater

Brandt’s Cormorant

Cooper’s Hawk

Steller’s Sea-Eagle

Harris’s Hawk

Swainson’s Hawk

Lewis’s Woodpecker

Williamson’s Sapsucker

Nuttall’s Woodpecker

Nutting’s Flycatcher

La Sagra’s Flycatcher

Couch’s Kingbird

Cassin’s Kingbird

Hammond’s Flycatcher

Say’s Phoebe

Bell’s Vireo

Hutton’s Vireo

Cassin’s Vireo

Steller’s Jay

Woodhouse’s Scrub-Jay

Clark’s Nutcracker

Bewick’s Wren

Pallas’s Leaf Warbler

Blyth’s Reed Warbler

Pallas’s Grasshopper-Warbler

Middendorff’s Grasshopper-Warbler

Townsend’s Solitaire

Bicknell’s Thrush

Swainson’s Thrush

Bendire’s Thrasher

LeConte’s Thrasher

Sprague’s Pipit

Pallas’s Rosefinch

Cassin’s Finch

Lawrence’s Goldfinch

Smith’s Longspur

McKay’s Bunting

Pallas’s Bunting

Botteri’s Sparrow

Cassin’s Sparrow

Bachman’s Sparrow

Brewer’s Sparrow

Worthen’s Sparrow

Harris’s Sparrow

Bell’s Sparrow

LeConte’s Sparrow

Nelson’s Sparrow

Baird’s Sparrow

Henslow’s Sparrow

Lincoln’s Sparrow

Abert’s Towhee

Bullock’s Oriole

Audubon’s Oriole

Scott’s Oriole

Brewer’s Blackbird

Swainson’s Warbler

Lucy’s Warbler

Virginia’s Warbler

MacGillivray’s Warbler

Kirtland’s Warbler

Grace’s Warbler

Townsend’s Warbler

Wilson’s Warbler

Morelet’s Seedeater

There are also several hybrids (e.g. Brewster’s and Lawrence’s Warblers), prominent subspecies (e.g. Thayer’s Gull and Audubon’s Warbler), and superspecies (e.g. Traill’s Flycatcher) that are used in some databases. It is not clear if these will be addressed at this time.

Birders detect dramatic changes as Davis climate warms

[A version of this was originally published in the Davis Enterprise.]

In 2002, the cover of The New York Times Magazine featured a silhouetted man standing on frosty mauve ice and staring through binoculars into a rosy polar sky. The title read, davis1“Watching the World Melt Away: The future as seen by a lonely scientist at the end of the earth.” The article was about seabird biologist George Divoky and his decades of work studying the black guillemot, a high arctic seabird, on Cooper Island off the coast of Barrow, Alaska. The guillemots were struggling to feed their chicks. Their preferred food, Arctic cod, lived at the edge of the sea ice. In the past, this was five miles from the island. Now it was thirty. Divoky, moreover, found himself sharing his tiny island with several hungry polar bears stranded by the vast expanse of open water. At the time, the story was one of the first concrete examples of climate change impacting an ecosystem in way that was easily seen and understood.

Sac Valley winter avg temps SH

Sixteen years later, birders in Yolo County are now witnessing those kinds of changes at our latitude. Winters are suddenly filled with species previously associated with warmer climates to the south, while some other winter visitors no longer come this far south. In the summer, new species are arriving from more arid regions and have started nesting locally.

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Orchard Oriole in Davis, December 2017

A shift of a few degrees may not seem like much, but a winter above freezing makes autumn fruit and berries available longer, resulting in a plentiful food supply. This past December, birders were astounded to find eight species of warblers and three species of orioles in the county at once. Normal would be three and zero, respectively. These birds are neotropical migrants, spending the summer nesting in the northern United States and Canada, and wintering in Southern California, Mexico, or Central and South America. In the last few years, Cassin’s vireos, black-throated gray warblers, and blue-gray gnatcatchers have been present at many locations throughout the cold months. It is now possible to find hooded orioles and western tanagers year-round. Last winter, rarities like orchard oriole, northern waterthrush, and palm warbler turned up and stayed for weeks or months. The prevalence of unusual over-wintering migrants has enabled birders to rack up quite a winter list. Holly Coates shattered previous “big year” records by tallying 200 species in Yolo County by March 20 this year.

neotrop migrants graphThe Putah Creek Christmas Bird Count, an annual effort to count all the birds in a 15-mile diameter circle near Winters on one day each December, has tracked winter bird populations since 1971. In recent years, the number of neotropical migrants found on the count has swelled. These include warbling vireo and Wilson’s and Townsend’s warblers, in addition to the species mentioned above. Perhaps the most dramatic shift in the count data has been with the turkey vulture. With the absence of tule fog, these birds, which rely on warm thermals to give them some lift, have gone from sparse, rarely more than 15 birds on a count through 1985, to over 150 individuals per count in each of the past eight years.

turkey vulture graphA warming climate is expected to create more increases than decreases in bird life in Yolo County. This is because species diversity is greatest in the tropics. As bird ranges shift north, we expect to see more arrivals than departures. Among the departures are some northern species that are growing scarcer in winter. Most notable is rough-legged hawk, a tundra species that journey south to agricultural areas to eat rodents in winter. They have, however, become decidedly hard to find in recent years, perhaps finding the Willamette Valley and other more northern valleys suitable for their wintering grounds. Another species to watch is the beautiful cedar waxwing, which descend on fruits and berries in the winter months. The more they can find food in the north, the less likely they will come this far south.  They are erratic from year to year, however, so it is too early to identify a trend.

Though less dramatic, our hotter summers have brought some changes as well. Great-tailed grackles have expanded up the Central Valley from the Salton Sea. Say’s phoebes, which previously nested only south of the Delta in the Central Valley, moved into Napa and Solano Counties in 2014. Perhaps they are focusing on certain species of insects. This spring, Michael Perrone found them nesting in Davis and Joan Humphrey discovered them feeding young in Woodland, representing first nesting records for the county.

The Yolo Audubon Society is currently revising its Checklist of the Birds of Yolo County, a useful little booklet that will list all 369 species recorded in the county, each with a bar chart showing their abundance through the year. The last version, published in 2004, had a special section called “Recent Changes” highlighting the wetland restoration projects at the Yolo Bypass Wildlife Area and Davis Wetlands. In the coming 2018 version, the Recent Changes section will focus on two big issues: the expansion of orchards and our changing climate. Perrone, author of that section, states that “winters have become milder. In particular, prolonged periods of cold, all-day tule fog have ceased, giving way to sunnier weather.” Davis birders may not be standing on the edge of the continent looking at retreating sea ice, but nevertheless, in the last few years they have witnessed dramatic changes in bird distributions. A look at the graphs, moreover, suggests these changes began before that article about Alaska was published.