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Spotted Towhee subspecies in the Pacific Northwest: From nearly-spotless to pretty messy

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There are 21 subspecies of Spotted Towhees, but only three of them occur in the Pacific Northwest. Even then, there is confusion.

Our local oregonus birds, like so many PNW subspecies, are dark and dusky. I call them Nearly-spotless Towhees. But sometimes in winter we see more spotted ones. In my quest to uncover the differences between curtatus and arcticus, the most likely candidates, I discovered there are more questions than answers.

Figure 1: The breeding ranges of oregonus, curtatus, and arcticus, the only three subspecies that occur in the northern US and southern Canada. The data (in red) is from summer eBird reports. The solid lines reflect the crude subspecies map in Birds of the World (in Figure 2 below). The dotted lines and question marks were added by me; the dotted lines reflect obvious breaks in breeding densities along the Continental Divide, rather than transecting riparian corridors where there are lots of towhees. An analysis of their songs (at the bottom of this post) suggest my dotted lines are more accurate, and the breeding birds in interior British Columbia, Washington, and Idaho are actually curtatus, not arcticus.

The confusion goes back to the 1800s. To quote from Rick Wright’s Sparrows of North America (2019), the taxonomy of Spotted Towhees is a source of “much confusion.” He’s actually quoting William Brewster from 1882. Yet, 137 years later, Wright spent the next 15 paragraphs describing decades of confusion – which persists to this day.

According to the Birds of the World (BOW) species account: “There exists no review of subspecies and no modern, quantitative study of geographic variation” outside of Mexico and the Pacific Coast (which was studied by Swarth in 1913). 

Because there are so many subspecies – some of questionable legitimacy – they are grouped. Even the groupings are confused.

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Figure 2: Spotted Towhee subspecies with BOW and Pyle groupings.

At present, BOW divides the 21 subspecies into 5 groups. Of relevance to the PNW, oregonus is in the oregonus Group, curtatus is in the maculatus Group, and arcticus is by itself, presumably because it the only Spotted Towhee that is entirely migratory and it also shows the most sexual dimorphism – that is, the female arcticus is quite distinctive.

(There are other Mexican subspecies separate from all of this, such as soccorroensis, which has been considered a separate species altogether.)

Because eBird uses the BOW approach, birders in PNW coastal regions encountering a heavily-spotted Spotted Towhee typically see these options on their app:

By “maculatus Group,” eBird, at least in the PNW, implies curtatus. Though arcticus is not listed, it does tempt birders to figure out how to distinguish arcticus from curtatus, because simply using “maculatus Group” on eBird implies the bird is not arcticus.

Oregonus is largely resident (though some go south in winter). Curtatus retracts from the northernmost part of its breeding range. Highly migratory, arcticus winters entirely south of its breeding range. Both are candidates to visit the West Coast of Cascadia, though curtatus is far more likely.

Despite its proximity (and the BOW range map), there are no confirmed eBird records of arcticus in Washington, and Wahl et al (2005), Birds of Washington, assert only oregonus and curtatus are expected. British Columbia has just two winter records for arcticus (2014 and 2016), both from south Vancouver Island, and one July record from just north of the Washington/Idaho border (perhaps based on the BOW map?).

Peter Pyle’s Identification Guide to North American Birds, 2nd Edition (2023) suggests a very different taxonomy (though tentative, as we all still await a DNA study). His 1st edition was similar to BOW, but even then he had arcticus with curtatus in what he called the Interior Group. In his 2nd edition, oregonus is limited to just itself; the rest are in the coastal megalonyx Group. (Peter tells me he’s suggesting reducing Spotted Towhee’s 21 subspecies down to seven, based on morphology.) As with his 1st edition, all the interior subspecies north of Mexico City are in the same group, which he now calls the arcticus Group. The maculatus Group is reduced to just four subspecies in southern Mexico and Guatemala.

By putting curtatus and arcticus together in the same group (and suggesting they be merged?), Pyle makes our lives easier – we don’t need to worry about the identification challenge to use the eBird subspecies offerings. Except Pyle calls it the arcticus Group, while eBird calls it the maculatus Group.

Let’s set aside the taxonomic and range map questions. Can we even tell them apart? Answer: sometimes.

Identification

Focusing on oregonus, curtatus, and arcticus, I’m relying on BOW, Wright, Pyle 1st and 2nd editions, photos on eBird, and personal observations (at least for the first two subspecies). Note that upperpart color tone varies depending on lighting, and the differences are subtle. Likewise, dorsal spotting appears to vary tremendously across individuals, and varies with angle of view and posture of the bird due to feather ruffling. Tail spots (the big white spots on the underside) may be the most definitive, yet there is overlap between forms and often they are difficult to see.

These sources also discuss how pale or bright the rufous flanks are. I’ve not included this, as the photos seem quite variable in this regard, probably due to lighting.

Of all the Spotted Towhee subspecies, Sibley only illustrates oregonus (which he calls the Pacific Northwest form) and arcticus (the Great Plains form), the least- and most-spotted forms.

 oregonuscurtatusarcticus
Upperpart color toneMale: glossy black; any streaking/mottling variable, but often quite limited.
Female: dull black, sometimes with a hint of brown, with faint bold black and dark gray streaks on the back.		Similar to oregonus, but less glossy, more flat black in male.  Male: dull to grayish black with bold black and gray streaks on back. Faint olive tone to rump. Female: brownish; with narrow blonde streaks on back.
Dorsal spottingWhite spots largely limited to the shoulder area, with a line of white spots along the scapulars; back largely dark.White spots coalescing into bright white streaks in shoulder area, with smaller spots extending onto back.Similar to curtatus with even more white spotting.
Tail spotsAbout ¼ to 40% the length of the tail. (Pyle: 12-25 mm long on r6)About 1/3 to ½  the length of the tail. (Pyle: 22-35 mm long on r6)Can be ½ the length of the tail or more. (Pyle: 27-42 mm long on r6)
The National Geographic Society guide, 3rd edition, illustrates these tail spots and undertail coverts – dark in oregonus; paler in every other form. I assume curtatus would be similar to montanus. Note that tail spot sizes have considerable variability (see chart above). Thanks to Dave Irons for alerting me to this illustration.

The photos below are mine or from eBird. It is frustratingly difficult to find photos of females in summer when they should be on their breeding range, and thus known.

Figure 3a: oregonus male; Port Townsend, WA; 6 Jan 2022. A typical nearly-spotted look. Note slight mottling on back.
Figure 3b: oregonus male; Port Townsend, WA; 4 Mar 2024.
Figure 3c: oregonus male; near Issaquah, WA; 21 Jun 2019 (from https://ebird.org/checklist/S67832978 Glen Chapman). This is bird showing a lot of white.
Figure 3d: oregonus male; Port Townsend, WA; 27 Jun, 2023 (from https://ebird.org/checklist/S142894263 Michael Long). Illustrating rather small tail spots, only about 1/4 the length of the tail.
Figure 3e: oregonus male; Port Townsend, WA; 16 Mar 2024. This one has larger tail spots, about 40% of the length of the tail, which would overlap with curtatus. But the undertail coverts are dark rufous.
Figure 3f: oregonus female; Port Townsend, WA; 10 Mar 2024. A typical female, showing some back streaking, visible in good light.
Figure 4a: curtatus male; near La Grande, OR; 30 Jun 2023 (from https://ebird.org/checklist/S143142401 Glenn Pannier). Much more boldly streaked white than any oregonus.
Figure 4b: curtatus male; near Summer Lake, OR; 25 Jun, 2012 (from https://ebird.org/checklist/S100771094 Scott Carpenter). Note the tail spot, nearly 1/2 the length of the tail, and the undertail coverts are paler.
Figure 4c: curtatus female; south of Asotin, WA; 25 May, 2023 (from https://ebird.org/checklist/S139221422 Dave Koehler).
Figure 5a: arcticus male; near Crawford, NE; 15 Jun 2019 (from https://ebird.org/checklist/S57397630 Steven Mlodinow). Note the tail spots over 1/2 the length of the tail, and the paler undertail coverts.
Figure 5b: arcticus male; South Sioux City, NE; 27 Oct, 2022 (from https://ebird.org/checklist/S121410819 Bill Huser). Note the boldly streaked back, though this bird is currently showing only modest white spots, which could be due to ruffled feathers. Many arcticus pics on eBird are wintering in areas where Eastern Towhee occurs. That’s why they got their picture taken and were identified to subspecies.
Figure 5c: arcticus male; south of Bismarck, ND; 16 Jun, 2021 (from https://ebird.org/checklist/S90269105 Ted Wolff). Note the large white tail spots, well over 1/2 the length of the tail.
Figure 5d: arcticus female; near Dickinson, ND; 4 May, 2018 (from https://ebird.org/checklist/S45246538 Jesse Kolar). Note the brownish hood and buffy streaks on the back.
Figure 5e: arcticus female; Ontario, CAN; 12 Feb 2021 (from https://ebird.org/checklist/S81352507 Brad Carey). Another out-of-range arcticus pic, illustrating the distinctive fawn brown female with buffy streaking on the back.

Songs

An analysis of songs of their songs suggest a different story — that oregonus and curtatus are very close to each other, but arcticus is quite separate, and with aspects similar to Eastern Towhee.

Spotted Towhees give two types of songs: a buzz or trill; and a slower electronic rattle or what I call the “shaka-shaka” song (example: https://macaulaylibrary.org/asset/587645701). I focus only on the former, and limit my window to May thru July, focusing on breeding birds in their summer range. They all give a distinctive “mew” call, quite different from Eastern Towhee, and rarely a few odd calls, such is a sharp “piew” that sounds like an Evening Grosbeak (example: https://macaulaylibrary.org/asset/447207011)

On to the buzz or trill songs. There are basically three different types:

  1. The buzz (dark green on the map). Example: https://macaulaylibrary.org/asset/584320661. This is often too fast to see the distinctive notes (vertical lines) on an eBird sonagram, unless it’s a very high quality recording. It seems more common on the Pacific slope (thus, oregonus), but is also given in the curtatus range. I could lump #1 and #2 here, as there seems to be a cline between them.
  2. The fast trill, often with a high-pitched introductory accent note or squeak (light green on the map). Example: https://macaulaylibrary.org/asset/464938911. The accent note seems more common and pronounced in the interior (the curtatus range). The same bird can give both the buzz and the fast trill.
  3. The trill with 2 to 6 sweet or scratchy intro notes, or even an intro trill (light blue on the map). Example: https://macaulaylibrary.org/asset/104621711. This song is the only one recorded on eBird in the arcticus zone, and it may be diagnostic for arcticus. Birds further east and around the Black Hills seem more likely to have more than two intro notes or an intro rattle. This song can be quite similar to Eastern Towhee, though Eastern typically has two different intro notes. With arcticus, the intro notes are alike. I found one exception, an arcticus with two different intro notes: https://macaulaylibrary.org/asset/220722981.

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Figure 6: Trill songs by type, as posted to eBird, using only data from May – July, all years.

The map of song types also suggests the BOW map of subspecies is indeed off. The song type I’m associating with arcticus seems largely limited to east of the Rockies, though it does cross the Continental Divide and extend further west near Idaho Falls and also into eastern Utah near Dinosaur National Monument (not on map). That is beyond the scope of this post.

Summary

A heavily-spotted Spotted Towhee in western British Columbia or Washington, presumably in winter, is far more likely to be curtatus than arcticus. In eBird you would choose “maculatus Group,” even though, for Pyle, that would mean a form from Oaxaca or further south. Identification can be made by the back spotting and size of tail spots, though both are subject to overlap in appearance.

Figure 7: apparent curtatus male; Port Townsend, WA; 22 Nov 2022. Out-of-range winter bird in my backyard.

arcticus vs curtatus

arcticus can be separated from curtatus if: 1) it sang its distinctive song (unlikely in winter?); 2) the tail spots were large, more than 1/2 the tail length; 3) this was supported by a streaked back; and/or 4) it was a female, which are distinctive.

Thanks to David Bell and the Cascadia Advanced Birding Facebook group for alerting me to Pyle’s treatment of these birds, and for inspiring me to do this deep dive. And thanks to all who posted pics and audio to eBird! I’ll never looks at towhees the same again.

References

Bartos Smith, S. and J. S. Greenlaw (2020). Spotted Towhee (Pipilo maculatus), version 1.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.spotow.01

Dunn, J.L. and Alderfer, J. eds., 1999. Field guide to the birds of North America, Third Edition. National Geographic Books.

Pyle, P., 2023. Identification guide to North American birds: a compendium of information on identifying, ageing, and sexing” near-passerines” and passerines in the hand. 2nd Edition. Slate Creek Press.

Pyle, P., 1997. Identification guide to North American birds: a compendium of information on identifying, ageing, and sexing” near-passerines” and passerines in the hand. Slate Creek Press.

Wahl, T.R., Tweit, B. and Mlodinow, S., 2005. Birds of Washington.

Wright, R., 2019. Peterson reference guide to sparrows of North America. Peterson Reference Guides.

eBird Trends maps reveal dramatic northward range shifts in Eastern species

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Over a year ago, on a webinar hosted by the Washington Ornithological Society (WOS), John Fitzpatrick of Cornell Lab of Ornithology teased us with some screenshots of eBird Trends maps. I was mesmerized. Now, they have been released here at the eBird Science tab. These remarkable maps illustrate population trends for each species across their range, showing exactly where they are increasing (blue dots) or decreasing (red dots).

They do more than that, actually. The color of the dot is correlated to the rate of change — the % change between 2007 and 2021. Dark blue means really increasing; dark red really declining. The size of each dot is correlated to the size of the population in that area (or “relative abundance” in eBird lingo). Big dots mean there’s a lot of birds there, regardless of whether they are increasing or decreasing. If you hover over a dot, the actual numbers pop up. White dots mean the data are inconclusive or show no trend. You can read more of the details at the site, and perhaps I’ll discuss methodology on a later post.

Here’s the amazing thing — each dot represents a 27 x 27 km (16.7 x 16.7 mile) grid square, so just a bit larger than a Christmas Bird Count circle, which are 15 miles in diameter. That’s a remarkable level of detail. I joke that there’s more information in these maps than in all the ornithological research in the last ten years. That’s an overstatement, of course, because professional ornithologists study things that eBirders don’t. Nevertheless, these maps take crowdsourced data collection and present it in ways that are instantly useful for understanding species population trends at a granular level. This has profound implications for targeting conservation.

So, on to my first of probably many posts looking at these maps. My first peruse suggests they strongly support what the climate change research has been saying — that resident and short-distance migrants are shifting their ranges north. Let’s start with some common eastern species.

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To examine each map in detail, go to eBird’s Trends page, type in the species name, and then click “Trends” to the right of the species’ name.

Until now, most of the published literature on northward range shifts have been meta-analyses with conclusions such as “non-migratory species are shifting north by so many km per year”, but no maps, nor even mention of species by name. Here, we get the details in bright colors, at the species and even county level. Wow.

A few observations. For many species, they are declining where they are still common (the red dots are large), and increasing where they are less common or even rare (the blue dots are small). This probably implies that their overall population is declining. It also suggests that climate change may be hurting them in the south faster than it is helping them in the north. It takes time to establish new populations, and/or the new regions may not be as suitable as their old home. Note also that each of these species have different transition isoclines (if that’s what one would call it). For example, Red-bellied Woodpecker and Carolina Wren are increasing in Tennessee, but Tufted Titmouse are declining there.

Here are some relevant papers regarding range shifts in eastern species, but again, these maps communicate their results in new and vibrant ways:

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. 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.

Rushing, C.S. et al. 2020. Migratory behavior and winter geography drive differential range shifts of eastern birds in response to recent climate change. Proceedings of the National Academy of Sciences, 117(23), pp.12897-12903. Since the early 1970s, species that remain in North America throughout the year, including both resident and migratory species, appear to have responded to climate change through both colonization of suitable area at the northern leading edge of their breeding distributions and adaption in place at the southern trailing edges.

Saunders et al. 2022. Unraveling a century of global change impacts on winter bird distributions in the eastern United States. Global Change Biology We conclude that climate has generally governed the winter occurrence of avifauna in space and time, while [habitat] change has played a pivotal role in driving distributional dynamics of species with limited and declining habitat availability.

The maps also support some of my previous blog posts: such as the northward expansion of Northern Cardinal, Carolina Wren, Tufted Titmouse, and Red-bellied Woodpecker, the crash of Florida’s white-eyed Eastern Towhees, certain range expansions of the Lesser Goldfinch and California Scrub-Jay, the expansion of many species from California into the Pacific Northwest, and the failure of oak-dependent species (e.g. Oak Titmouse and Nuttall’s Woodpecker) to go anywhere.

In future posts, I’ll look at range shifts in resident birds of the West, the impact of California’s fires (many encompassing several of these Trends dots), long-distance migrants, nationwide species, waterbirds, and seabirds, among other things.

Eastern Towhee: Can the white-eyed subspecies survive even 1.5C climate change?

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Pale-eyed and red-eyed forms diverged approximately 18,000 years ago.
Photo by Melissa James/Macauley Library.
eBird abundance map for Eastern Towhee. It is resident in the southeast, but expands north in summer.

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%.

This is National Audubon’s projection for the Eastern Towhee’s breeding range under just a 1.5C scenario. This would spell extinction for the white-eyed birds of Florida and the deep South.
Their winter range is not anticipated to change much.

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.

eBird data from Florida, focusing on frequency of lists reporting the species during the May-June period, shows that the maximum frequency has fallen from 18.3% in 2015 to 8.6% in 2021.

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.

Photo from National Audubon website that provides range change projections under 1.5C, 2.0C, and 3.0C scenarios.

For more on climate change impacts on birds, I invite you to join the Birds and Climate Change Facebook group.