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“Russet-backed” vs. “Olive-backed” Swainson’s Thrushes

“Russet-backed” vs. “Olive-backed” Swainson’s Thrushes

"Olive-backed" Swainson's Thrush, Bismarck, North Dakota, 5/8/2009. Discovered in a storage shed, it was photographed before being released. Photo by Matt Reinbold (CC-by-sa).

The April 2013 issue of Colorado Birds recently hit my mailbox. It’s an excellent issue of a top-flight regional birding journal, and I’m particularly excited about the article about identifying the two distinctive subspecies groups of Swainson’s Thrushes: “Russet-backed” birds from the Pacific Northwest, and “Olive-backed” birds from elsewhere in the range.

(In case you’re wondering about the source of my enthusiasm, I should mention that I not only edit the journal, but also co-authored the article, with the eminent Steve Mlodinow and Tony Leukering.)

I grew up seeing hundreds of Swainson’s Thrushes in South Dakota each spring — all birds of the “Olive-backed” persuasion, though I had no idea of that at the time.  When I encountered my first “Russet-backed” Thrush in northern California in 2000, I was certain I was looking at a Veery.  The uniform, rich chestnut-brown upperparts ruled out all other thrush species, or so I thought at the time, and it wasn’t until many years later that I realized my mistake.

Over the past decade, the work of Kristen Ruegg and her colleagues has shown that the two forms of Swainson’s Thrush not only look different, but migrate on different schedules to markedly different wintering grounds. They hybridize in a contact zone in British Columbia, but that contact zone is quite narrow, prompting occasional rumors and rumblings of a potential future species split.

One of the proposed lines of evidence concerns differences in vocalizations.  And, with some cribbing  from the Colorado Birds article, that’s what I’ll be writing about today.

Differences in song?

A 2006 study by Ruegg et al. claimed that the songs of “Russet-backed” and “Olive-backed” Thrushes differ in statistically significant ways.  The spectrograms in the study seem to indicate some nice obvious differences:

Song spectrograms of "Russet-backed" (left) and "Olive-backed" (right) Swainson's Thrushes, from Ruegg et al. 2006, Fig. 3. Each top-bottom pair (e.g., 1.1 and 1.2) represents two songtypes of one individual.

When I first laid eyes on this figure, I thought this ID should be a cinch.  The Russet-backed songs in the figure are much longer on average (song 1.1 is just under 2.5 seconds long, while song 4.2 is under a second), and they finish with high, fluting, polyphonic phrases like those in a Veery song, while the Olive-backed songs stay relatively low and simple.

But when I looked at a scattering of songs from across the country, it quickly became clear that these differences did NOT hold up across the species’ entire range.

“Russet-backed” “Olive-backed”

Obviously the Olive-backed songs from elsewhere on the continent seem just as likely to go on longer and end in high, fluting flourishes.  I’ve listened to a large number of songs of both species, and I can’t find any way to distinguish them by ear.

To be fair, Ruegg et al. weren’t just looking for differences obvious to the eye and ear — they were performing quantitative analyses based on spectrographic measurements.  Even so, they recorded songs from just two coastal populations and two inland populations (plus a fifth population in the hybrid zone).  Their results may be due to the differences between the local dialects of these few regions, rather than any larger or more consistent difference between the subspecies groups.

If anybody knows of a way to identify the songs of these two groups by ear, I’d love to hear about it.

Differences in calls

I am unaware of any consistent differences between the “wee?” flight calls of the two subspecies groups, which is a mellow rising whistle rather like the call of the Spring Peeper frog. The “quit”-type contact call, however, does seem to differ slightly on average.  Olive-backed tends to give a quick, sharp “quit” that may recall the sound of a dripping faucet or the “whit” of an Empidonax flycatcher. In Russet-backed, this call is often slightly longer and more musical, an obviously upslurred whistle that might be transliterated as “wee” or “pwee,” like a shorter, sharper version of the flight call.

These examples are illustrative:

“Russet-backed” “Olive-backed”

Even this slight difference, however, cannot always be trusted.  One recording I found documents a “Russet-backed” from northern coastal California who gives, in between his songs,

  • a series of “typical” contact calls of Olive-backed Thrush (1:25 – 1:50);
  • a series of “typical” contact calls of Russet-backed Thrush (2:20 – 2:35); and
  • a wide variety of “flight calls” (0:37 – 0:43, 2:49, and 3:43 – 3:48).

At least some individual Olive-backed Thrushes give equally variable calls, so caution is in order.

Perhaps the most distinctive vocalization is the alarm call, which is a two-part sound ending in a low, loud, semi-musical purr or chatter. Olive-backed tends to introduce the chatter with a sound like the contact call, “quit-BRRR,” while Russet-backed tends to begin with a much longer and more musical note that is actually more like the flight call: “weee-BRRR.”

“Russet-backed” “Olive-backed”

On the whole, the differences in voice between these two subspecies groups are pretty subtle, and almost never diagnostic, due to extensive variation within each group. I recommend using voice as a supporting character in the field, to be used in conjunction with visual field marks.


More on the Mystery Empid Call

More on the Mystery Empid Call

A few months ago I wrote about a mysterious new “whit-beert” call that I had discovered in the bowels of the Macaulay Library’s online collection, and which I took to be a previously undescribed sound of Yellow-bellied Flycatcher.  Noticing a certain resemblance to the “dew-hic” call of Dusky Flycatcher and the “peer-pewit” call of Hammond’s Flycatcher, I concluded that the new call was likely homologous with those sounds — that is, that the “dew-hic,” the “peer-pewit”, and the “whit-beert” are all evolutionarily derived from a similar call given by the species’ common ancestor.

Now, new information has come to light that calls my earlier conclusions into question.  First of all, Empid guru Arch McCallum told me he wasn’t convinced that the “whit-beert” was equivalent to “dew-hic” and “peer-pewit”, due to the different spectrographic shape of the “whit” and the fact that it was never repeated.  Instead, he pointed out the similarity of “whit-beert” to certain calls of Willow and Alder Flycatchers.

He may have hit the nail on the head.  I recently discovered a second recording of the mysterious “whit-beert,” from western Maine, labeled as an Alder Flycatcher.

“Whit-beert” call, labeled as Yellow-bellied Flycatcher.
Woodhull Lake, New York, 5/30/1998. ML catalog #106901
“Whit-beert” call, labeled as Alder Flycatcher.
Upton, Maine, 6/2/1962. ML catalog #7546

The new recording was taken in 1962, before “Traill’s” Flycatcher was split into Willow and Alder. The recordist was Dr. Robert C. Stein, who had already realized that “Traill’s” sorted into two vocal groups, and was in the process of collecting data for his classic 1963 publication that provided the first strong evidence for the eventual species split.  The notes on the recording indicate that the recording was made during a “hostile response to playback,” but it doesn’t say what sound was used for playback, nor does it explain how the recording was identified as an Alder Flycatcher.

So: which species is it that gives the “whit-beert” call?  Personally, I agree with Arch that Yellow-bellied is probably the least likely culprit.  Alder is the leading contender at the moment, followed by Willow.  But to answer the question definitively, I think we’ll need some more recordings.

If you’re interested in helping to solve the mystery, you might try some playback experiments in northeastern North America this spring.  Does playing “whit-beerts” to an Empid elicit more “whit-beerts”?  What species says “whit-beert,” and what is the behavioral context of the sound?

I don’t think anybody knows the answer to the questions I just asked.  I don’t think anybody has ever known.  But they could be easily answered by anyone with an audio recorder and a couple of spare hours in New England this summer.

This is what I love most about bird sounds — the tantalizingly short distance to the frontier of knowledge.

Greater vs. Lesser Yellowlegs

Greater vs. Lesser Yellowlegs

Lesser Yellowlegs, Jamaica Bay National Wildlife Refuge, NY, 9/30/2007. Photo by Wolfgang Wander (GFDL).

Can you tell Greater and Lesser Yellowlegs apart by voice?

Can anybody?

A recent thread on the Xeno-Canto forum started me asking questions about how to identify yellowlegs by voice.  Conventional wisdom says the two species can often be separated by their calls, at least with some experience.  But as I was comparing the many online recordings, I came to an uncomfortable conclusion.  Either an awfully high percentage of the recordings were misidentified, or my own identification criteria were wrong.

Today, I invite you to either share my confusion, or help me sort it out.

History of the problem

In the old days (i.e., the 20th century), identifying yellowlegs by voice was simpler.  Back then, according to the field guides, all you had to do was count the notes:

Field guide Greater Yellowlegs Lesser Yellowlegs
Peterson Western (1961) A 3-note whistle, whew-whew-whew, or dear! dear! dear! You or you-you (1 or 2 notes), less forceful than clear 3-syllabled whew-whew-whew of Greater Yellowlegs
Golden (1983)
sharp 3- to 5-note whistle soft 1- to 3-note whistle that lacks the loud ringing quality of the Greater’s
National Geographic (1999)
loud, slightly descending series of 3 or more tew notes higher, shorter than in Greater: 1 to 3 tew notes

Although all three guides suggest differences in pitch and/or tone quality, most people took away a simple rule: three or more notes is a mark for Greater Yellowlegs, less than three notes is a mark for Lesser. Everybody understood that this was a rule of thumb and not a universal law, but still, it was a very popular mental shortcut.

Then Sibley came along, and started complicating matters:

Greater Yellowlegs Lesser Yellowlegs
Sibley (2000)
Flight call a loud ringing deew deew deew; typically three or four notes; higher than Lesser with strident overtones. In agitation an endlessly repeated single note tew, tew…. Feeding bird gives soft, single notes. Display song a melodious, rolling kleewee kleewee…. Flight call of short whistles tip or too-too typically flatter and softer than Greater; usually only one or two notes. In agitation a repeated tiw, tiw…. Alarm a rising, trilled kleet. Threat a low, rolling trill. Display song a rapid, rolling towidyawid, towidyawid…; lower-pitched than flight call.

Here the numbers are tempered with the words “typically” and “usually,” and pitch and quality get a little more attention.  Most importantly, the yellowlegs are now presented as birds with large vocal repertoires — you have to be sure you’re listening to the “flight call” before you start counting.

So… how do you tell what you’re listening to?

The “classic” calls

Here’s a pair of recordings from the same location on the same date, by the same recordist, that fit all the classic descriptions of the two species’ “flight calls”:


Besides the number of notes, check out the huge difference in the shape of each note on the spectrogram.  Lesser gives a pretty simple downslurred whistle, while Greater has a much more complex pattern.  If you look carefully, you can see that each note of the Greater’s call contains an upward voice break.  This means each note is 2-parted, the second part suddenly jumping to a much higher pitch.  This happens so fast in each note that we still tend to hear the two parts as one, but the overall impression is very different from Lesser, more of a “klee-klee-klee” than a “pew-pew-pew.”  The higher second part of each note is what Sibley refers to as the “strident overtones” of Greater.

The alarm series

Both yellowlegs give loud, incessant calls in series when they are upset, year-round. In Greater these notes are noticeably rougher than the typical “flight call,” due to a brief burry or grating sound in the middle of each note. In Lesser, the notes of the alarm call strongly resemble the notes of the “flight call,” but marginally higher. They are perfectly clear, without any trace of roughness:

Where it gets complicated

Here’s the bad news. Based on a set of positively-identified recordings (mostly those that also contain examples of each species’ diagnostic song, in the Macaulay Library collection), it’s pretty clear that

  • the notes in Greater Yellowlegs “flight calls” don’t always break.
  • the notes in Lesser Yellowlegs “flight calls” sometimes do.
  • in both species, the number of notes in a “flight call” depends on the agitation level of the bird.

I don’t have any reason to believe these four recordings are misidentified. In fact, I was present for the recording of Andrew’s Dove Creek bird, and as I recall, it was seen well and its identification was uncontroversial.  All these examples sound like they’ve got Lesser’s tone quality and Greater’s note pattern, and without visual clues, I’m not sure they’re identifiable, even on the spectrogram.  Here’s another pair of examples:

 Greater Yellowlegs, from Macaulay Library 27042 (click to listen)  Lesser Yellowlegs, from Macaulay Library 26256 (click to listen; this vocalization is from the eighth minute)

There are some differences in pitch and inflection here, especially towards the end, but the opening notes are nearly identical, and match my expectations for the “classic” Greater Yellowlegs tone quality.

A gallery of confusing yellowlegs

I’m relatively confident about the ID of all the recordings I’ve posted so far, but I’m not at all sure about the ones that follow. The only thing I’m sure of is that an awful lot of yellowlegs recordings thwart my original expectations of both species.  Perhaps these next few recordings are all wrong, and yellowlegs identification isn’t as hard as I’m making it out to be! Perhaps they’re all or mostly right, and yellowlegs identification is very tricky indeed.

Any comments on the identification of these recordings, and yellowlegs vocal ID in general, would be greatly appreciated.

The “Tink” Call

The “Tink” Call

Bay-breasted Warbler, Rondeau Provincial Park, Ontario, 5/5/2007. Photo by Mdf (CC 3.0).

Not too long ago, it was commonplace for birders to make casual references to THE call or THE song of a bird species, as though every bird had only two modes of communication.  Now we know better.

These days, I’m more likely to hear casual references to THE flight call and THE alarm call.  After all, when we notice that, for example, many species of warblers and sparrows give similar high “seets” on the wing in migration and sharp “chips” in alarm when perched, it makes sense to group those calls into categories and name them after similarities in their form or function.

But there’s an odd, insidious trick of psychology at work in all of us.  If a sound doesn’t match our expectations — if it doesn’t fit one of our pre-existing mental categories — we’re much less likely to hear it.  If we do hear it, we’re likely to dismiss it as a quirk of the individual, a bird doing “something weird.”  Or else we’ll just cram it into a category we recognize: “must be the flight call, I guess.”

Something like this happened to me as I researched the “call notes” of various warblers.  I regularly ran into sounds that didn’t fit my mental categories, and after a brief period of confusion, I tended to dismiss them as atypical versions of the normal call.  Beware that word “atypical” — it strongly suggests that what you’re hearing is best ignored, that it’s an outlier at risk of messing up your dataset.

A few months ago, an online chat with my co-blogger Andrew Spencer started unraveling some of my preconceptions:

Andrew: are you going to cover alarm calls in warblers?

me: What kinds of alarm calls?

Andrew: those high pitched tink calls that many warblers give


I think every warbler just about does tink calls when alarmed

I heard Connecticut Warbler give one

and I’ve heard it from a number of other species

but I don’t know how many recordings there are

me: Just higher-pitched versions of the normal call? Or something distinct?

Andrew: the one I linked of the Orange-crowned Warbler is distinct I think

all the ones I’ve heard sound damn near the same

me: I remember when I was researching Louisiana Waterthrush calls I came upon a recording in the Macaulay collection of a bird giving calls much higher than all the other recordings — more like your tinks. I just figured it was a crazy variation on the normal call.

Andrew: I have calls like that from Black-throated Blue Warbler as well:

me: And I have a recording of an agitated Kentucky Warbler switching back and forth from a chip-like to a tink-like note.

Andrew: and I got a few from Golden-winged Warbler this past trip

me: These “tink” notes appear to be poorly described in field guides and the literature.

Andrew: doesn’t surprise me

me: This calls for a blog post.

Andrew: haha I was about to say the same thing

As soon as I started digging, I realized that these “tink” calls hadn’t gone unnoticed by everyone.  Paul Driver featured them on his blog back in 2009, under the name “high chip calls”:

A number of warblers (perhaps most?) have high chip alarm calls different to the typical chip call, sounding more like titmice or Golden-crowned Kinglet. They seem to be heard most often on breeding grounds and are often given by birds that are highly agitated; in this way they seem analogous to the high chip call of the Song Sparrow.

Funny he should mention Song Sparrow.  Recordings show that a great many species of sparrow give a “tink” note that sounds much like the “tinks” of warblers, and is given in similar situations of high alarm.  (This warbler-sparrow similarity is no coincidence – but that’s a subject for another day.)

These “tink” notes seem worth of their own category, separate from the “call” and the “flight call.”  They tend to indicate a higher level of alarm than “typical” calls, but not as high as the buzzes and shrieks that these birds give when they’re really upset (e.g., when a predator is attacking a nest, or when the bird is caught in a mist net).  Sometimes one hears calls intermediate between the high “tinks” and the lower “chips,” especially from sparrows.

“Tinks” can raise some interesting questions.  In some species, like Cape May Warbler, the “typical” call sounds much like a tink, and there may be little distinction — or is it perhaps that the tink is just more frequently given, so that we think of it as typical?  At the very least, if you happen to be in the habit of identifying Cape May Warblers by call alone, the existence of similar sounds in all these other species should give you pause.

An online catalog of “tink” recordings

Not every warbler and sparrow has a “tink,” apparently. For example, I haven’t been able to find any convincing examples from the genus Spizella (except for American Tree Sparrow, which many researchers agree is misplaced in Spizella and overdue for a move to its own genus).

I’ve attempted to assemble a collection of “tink” recordings that are available online, in order to document their existence in as many species as possible.  No doubt there are other “tinking” species not currently represented below.

If you can add to the list above, or have other useful observations of “tink”-like notes, let me know!

Learning Laplands

Learning Laplands

Lapland Longspur, Kodiak National Wildlife Refuge, Alaska. USFWS image in the pubic domain.

In wintertime, huge numbers of Lapland Longspurs come down to the northern United States from their Arctic breeding grounds — sometimes gathering in enormous single-species flocks, but often mixing with other longspurs, Horned Larks, and Snow Buntings. At a distance, their cryptic winter plumage pattern can make them hard to pick out from these other birds. That’s why many people “look” for longspurs with their ears.

Away from the Great Plains, Lapland is usually the only expected longspur species, and one can usually detect and identify it by its characteristic rattle call, which generally resembles the rattles of other longspurs.  Although the number of notes is highly variable, this call is pretty much the same across the Lapland Longspur’s entire (worldwide) range:

Lapland Longspur rattle, Weld County, CO, 11/19/2007.

But this isn’t all that longspurs say.  They give a variety of other calls, some of which are more immediately distinctive than the rattle.  Here in Colorado, I recorded a longspur giving “chewlup” and “terlee” calls in addition to rattles:

As I started listening to recordings of Lapland Longspurs from other parts of North America, I started to hear other types of calls.  Individual birds give at least 5 or 6 different whistled calls, especially on the breeding grounds, and individual repertoires seem to differ, especially from one geographic region to the next.  In trying to catalog Lapland Longspur calls, I ended up making a map of variation.  First, I found recordings from seven distinct locations where this species breeds in the North American Arctic:

  1. Seward Peninsula, western Alaska (LNS 49598 and LNS 141100)
  2. Denali National Park, central Alaska (LNS 50024)
  3. Colville River Delta, northern Alaska (LNS 131257)
  4. Babbage River, northern Yukon (LNS 61441)
  5. Bathurst Island, Nunavut (LNS 137341)
  6. Devon Island, Nunavut (LNS 61444)
  7. Baffin Island, Nunavut (LNS 61426)
Locations of the Lapland Longspur recordings

Then I went through the recordings and made a table showing the geographic similarities and differences in calls:

In the table above, all the spectrograms in a given row represent different calls from the same individual bird (except for the first row — the “chewlup” and “ter-lee” are from a different bird than the other three).  Here are the takeaway lessons:

  1. Some calls are clearly the same across wide portions of the range. For example, the call that sounds like “ti-turtle” is clearly the same in western Alaska, northern Alaska, and the northern Yukon.  But it does not appear in recordings from other regions — at least not in a recognizable form.
  2. This graph isn’t wide enough to show all the types of calls. In particular, the recordings from northern Alaska (#3) and Bathhurst Island (#6) contain multiple call types that I didn’t include because they didn’t seem to fit into any of the existing columns.
  3. Few, if any, of the whistled calls are truly universal. The only whistled call type that comes close to appearing in all regions is the “few,” and even then I’m not certain that the “fews” I illustrate above for Devon and Baffin Islands are really equivalent to the “fews” from elsewhere.  It’s possible that more recordings would change this, but note that the extensive recordings from northern Alaska and Bathurst Island show an almost complete lack of shared calls — and that includes the ones I left out for lack of space.
  4. Most, if not all, of the calls can be heard in winter as well as summer.  Though rather few recordings are available from wintering birds, it appears that the calls of longspurs wintering in western North America and on the Great Plains tend to resemble the those from Alaska (locations 1-3), while the calls of longspurs wintering in eastern North America tend to resemble those from Arctic Canada (locations 5-7).

What can we conclude from this information?  Well, for starters, it’s pretty clear that these calls are learned, not innate.  That would explain why birds from a given region tend to share call types, while birds from far away tend to sound quite different.  It fits a pattern of regional dialects that are typical of learned vocalizations.  Each bird learns not just one call typical of its region, but an entire set of regional calls — much like the Red-winged Blackbirds I discussed a while back.  In longspurs, like in Red-winged Blackbirds, dissimilar calls likely fulfill similar functions in different regions of the Arctic.  For example, longspurs expressing agitation at a human near a nest tend to cycle through 3-4 different call types — but the birds on Bathurst cycle through a totally different set of calls than the birds on the north slope of Alaska.

Obviously, people attempting to identify Lapland Longspurs by their calls in winter have their work cut out for them.  My general impression is that longspurs wintering in Colorado sound the same year after year, consistently giving “few,” “chewlup” and “ter-lee” calls like the northern Alaska birds above.  But if I went to, say, Iowa, the longspurs would be likely to sound rather different.

Much remains to be learned about the Lapland Longspur’s complex communication system.  I’m looking forward to knowing more.

North by Northwest

North by Northwest

"Northwestern" Crow. This crow from La Push, Washington (on the outer Olympic coast) is supposedly a Northwestern Crow according to various sources. But is it really? Photo by Andrew Spencer.

There are few species in North America as ambiguous as Northwestern Crow (Corvus caurinus).  Even in a group of birds that are exceedingly similar the differences between American Crow (Corvus brachyrhynchos) and Northwestern Crow are minuscule at best.  The only “surefire” way to tell them apart is by range; however a number of sources also cite vocal differences as a distinguishing characteristic (e.g., the Sibley Guide, some versions of the National Geographic Guide, Birds of North America).

American Crow is a very familiar bird to most people in the US – it occurs throughout the lower 48, except for certain areas near the Mexican border.  Northwestern Crow is typically described as being found from northwestern-most Washington state along the Pacific coast to Alaska, as far west as Kodiak Island and the adjacent mainland.  Outside of a narrow overlap zone in Washington state and southern British Colombia you can typically call the species by range alone.

But the situation is more complex than just being able to tick a bird for your list based on where you are.  The American Crows found along the Pacific coast (ssp. hesperis) are at the small end of the spectrum for the species, sometimes look slightly “shinier”, and have subtly but noticeably different voices than American Crows further east (as an aside, the official designation of what constitutes hesperis is murky at best, and birds from as far away as Utah or Colorado could be this subspecies depending on some readings of the literature).

For a long time I’ve had a theory that the real “Northwestern” Crow was actually a “Pacific” Crow, since the American Crows along the northern California and Oregon coasts  sounded and looked more like “Northwestern” Crows in Washington and further north, and different from the American Crows further east.  If this was true, I theorized, then the crows west of the Cascades in the more humid areas of Washington, Oregon, and California, were a different species than those east of the Cascades in the drier rainshadow of the mountains.

So on a few recent trips I’ve taken to Washington I’ve made an effort to record crows wherever I found them, including going out to what were supposed to be the most “pure” Northwestern Crows left in the state, on the San Juan Islands and along the outer coast of the Olympic Peninsula.  I also recorded some crows to the east of the Cascades, from the Okanogan Valley and further east.  What I was hoping to find was either that the supposedly pure “Northwestern” Crows had a notably different voice than the taxonomically ambiguous ones around Seattle and along the outer coast in southern Washington, OR that all the crows west of the Cascades had similar voices that were different than crows to the east.

Unfortunately, as often happens with research of this type, what I found was different than either ideal situation.  I’ve been able to hear what I feel are distinguishable differences between birds in Colorado and the ones in western Washington.  But when I compared birds I recorded to the east of the Cascades in Washington I begin to hear what sounds like the start of a cline to the birds in Colorado.  Recordings from further afield, in Oregon, California, and British Colombia seem to continue this cline.  On the other side of the spectrum, though, when comparing the crows at the northwestern end of the range of American Crow to Northwestern Crows from Washington and further north into Alaska I don’t hear any vocal differences.  This would seem to show that the end of the cline in crow vocalizations is not where the species boundaries are currently drawn.

When comparing the sounds from various crows it’s important to have an idea of what vocalizations each species makes.  Anyone who has ever listened to a crow knows they have a remarkably large repertoire, everything from caws to screeches to rattles to song-like warbles.  The most common calls, though, are variations on the “caw” call.  These can typically be lumped into two groups, long and short, but there is a nearly complete continuum between those.  Often within any individual bird the long calls sound lower and more nasal, so care has to be taken when comparing different individual crows and making assumptions about differences in pitch.  Here are two cuts from the same individual bird in Washington showing a long and a short “caw”.

Ok so now to start the comparisons – listen here to what I consider a “typical” American Crow call from most of the continent, first longer calls then shorter:

And here is what I consider a typical American Crow from the Seattle area:

And a few from further east in Washington:

And here are some American Crows from further south along the Pacific coast:

Also listen to ML#13108 from the Willamette Valley of Oregon, ML#118854 from Tulare County, California, and ML#58191 from Hedley, British Colombia, all inland locations.

The ones around Seattle to my ears sound a bit more nasal, and on average slightly lower pitched than the birds from east of Washington state.  It isn’t a huge difference, and there is some overlap, but whenever I arrive in Seattle after spending time in Colorado or further east I hear the difference.  The birds from Okanogan County to the east of the Cascades sound similar to the Seattle birds to my ear, but are starting to having a hint of an eastern “accent”, as are the birds from coastal California. The recording from Oregon, though, sounds more eastern to my ears, and the ones from Tulare County, California, and British Colombia sound eastern to me.

Now listen to the calls of putative “Northwestern” Crows, also from Washington:

Not very different, right?  And here are links to some Northwestern Crows in the Macaulay Library from further north, far enough away from American Crow to be pure, supposedly: ML#132185, ML#136466, ML#58198.

Also not very different from the American Crows in Washington!

There are still some potential wrinkles to work out.  Without knowing the sex of the crow recorded it’s hard to determine what potential differences in male and female voices there are and how that affects the variation.  And it’s hard to get a real handle on the complete variation in each population without more recordings.

Now I can’t comment on the distinctiveness of Northwestern Crow based on genetics, structure or plumage, or physiological differences.  But I would contend that despite what many field guides, and BNA say, there are no compelling vocal differences between that species and American Crows in the Pacific Northwest.  With this lack of a vocal dividing line there seems to be little support for drawing the species boundaries in their current location.  Add to that the apparent evidence of a cline between the crows in the Pacific Northwest and those east of the mountains to the birds even further east, and the evidence for having two species at all starts to look weak indeed.

The Dawn Song of Brown Creeper

The Dawn Song of Brown Creeper

Brown Creeper, Pueblo County, CO, November 2006. Photo courtesy of Bill Schmoker

The dawn chorus. You love it or you hate it.

If you hate it, it’s probably because you don’t appreciate being roused from sleep by a vigorous burst of birdsong in the early morning darkness.  This is a common sentiment in the parts of the world where we now think of nature as an interruption of our experience, rather than the medium through which it flows.

If you love the dawn chorus, it may be for its music, its regularity, its symbolism.  Or just for the happy reminder that nature survives, at least in some form, right outside the window.

I love the dawn chorus in part because it contains songs that you can hear at no other time of day.  A number of North American birds sing dawn songs unlike anything they say after sunrise. I’ve written here about several: Violet-green Swallow, American Robin, Cassin’s Kingbird, Cordilleran and Pacific-slope Flycatchers.  But if you had asked me six months ago whether Brown Creeper had a distinctive dawn song, I would have told you no.

Here’s the typical song of the Brown Creeper — a short high-pitched warble, repeated without much variation:

Most sources say that this song can be heard at any time of day.  Some observers have reported hearing it as early as 4:50 in the morning, but it doesn’t seem to be given regularly or repeatedly at that hour.  Instead, most Brown Creepers apparently start their day with utterances like this one:


Brown Creeper dawn song, Coos County, OR, 7/1/1990. Recording by Geoff Keller (ML 50337).

(Click here to listen to this recording at the Macaulay Library website.)

Two “tseew” notes followed by two “trill” calls may not sound like much of a dawn song, especially since the “tseew” and the “trill” are two of the common calls given by Brown Creepers throughout the day — the “tseew” mostly in alarm, the “trill” in a variety of situations.  But this is not just a string of calls mixed together at random.  The calls comprise a repeated and stereotyped sequence: “tseew tseew trill trill… tseew tseew trill trill… tseew tseew trill trill… tseew tseew trill trill.”   The exact pattern varies from one bird to the next, but each individual adheres to its own fairly rigid syntax and rhythm.  They’re not just calling, they’re singing.

Brown Creepers, unlike many other species, appear to transition gradually from dawn singing patterns into daytime singing patterns.  They start out with these stereotyped patterns of “tseets” and “trills” and then, as the sun rises, they start tossing in “regular” song strophes more and more frequently.  Here’s a sunrise recording from New Jersey in which the dawn songs and the day songs are alternated.  And here’s a dawn-singing bird from Arizona that introduces each strophe of day song with components of the dawn song:

I have a recording, also from Arizona, of a Brown Creeper doing something similar as late as 9:00 AM.  Later in the day, the dawn song patterns apparently disappear altogether.

More study of Brown Creeper dawn-singing is needed.  For example, it would be interesting to determine patterns of individual and geographic variation, and to find out whether and how birds respond to playback of the dawn song.  If you live near Brown Creepers, it wouldn’t be too difficult to find answers to some of these questions next spring — as long as you’re willing to rise before the birds.

Video Library: Large Gulls

Video Library: Large Gulls

The internet is full of wild bird videos.  If you want to learn about behavior and vocalizations, it can be a great place to start, at least for certain species.  Gulls are a terrific example.  They’re loud, they’re conspicuous, they’re tame, and when engaged in their behaviors, they ignore gawking humans with videocameras.  I was able to observe more behaviors from more gull species in a few hours on YouTube than I could have seen in a couple of weeks at the beach.

Today, I share the fruits of my labors, categorized by species and behavior type.  This is nowhere near comprehensive — each time I go back to the internet, I find more videos worth including.  I’ve had to limit this to the large gulls (genus Larus) for now, and even so, many species aren’t even represented here at all yet. If you find footage worth including, please leave a comment or shoot me an email and let me know.

For an introduction to the gull behaviors mentioned here, see my last post.  Enjoy!

American Herring Gull

Cornell’s “How Nature Works: Gull Territoriality” — a good overview of gull behaviors, starring mostly Herring Gulls and a few Great Black-backeds

Aggressive encounter with “mew” duet, “choking” display, and fighting. Connecticut, late fall.

Pair of Herring Gulls giving head toss / courtship begging calls, then copulating (loud narration by people nearly throughout)

Copulating pair in Rhode Island (voices of birds hard to hear)

Two juvenile Herring Gulls giving begging calls (July, Saskatchewan)

Glaucous-winged Gull (and/or intergrades)

A pair of apparent Glaucous-wingeds in a park in Washington State in spring — probable courtship behavior, including Mew calls.

A pair-bonding display between two Glaucous-wingeds or possible intergrades: one bird (perhaps the female) gives the Head toss / food-begging call, and the other bird regurgitates a fish

Pair on streetlight, head-tossing, with some begging bill pecks, and accompanying calls; species ID not clear

Western Gull

Pair of apparent Western Gulls giving Mew calls, perhaps some “Choking” displays, then fighting at end:

Solo Western Gull giving a few Mew calls. Catalina Island

Pair fighting with bills locked, apparently without vocalizing; then they break apart and give multiple Long Calls; then a more violent, briefer fight; then the victor struts around giving some low grunts and a final Long Call

Six nice food-begging calls given with head-tosses by one member of a pair on Alcatraz

Female giving head-toss begging call; male quickly mounts; eventually copulation begins accompanied by male copulation grunts. Audio rather terrible. Near Fisherman’s Wharf, San Francisco.

Copulation with decent audio of male copulation notes. Start and end not shown. La Jolla, California

Copulation; video rather brief but audio decent, with the exception of one comment in middle by videographer

Two Western Gulls fighting in parking lot, giving kek-kek calls (alarm chuckles) constantly. Video from second-story deck with commentary.

Heermann’s Gull

Two nice Long Calls, display postures and all, from one individual

Very brief video of some rapid nasal series, including some possible Long Calls

Iceland Gull

Iceland Gull calls once, rather faintly, near the end of this video (short low nasal bark):

Lesser Black-backed Gull (subspecies graellsii or similar)

One nice Long Call with full display postures, Liverpool, UK:

Closeup of a bird giving alarm chuckles and one Long Call with medium-strong display postures; a little disruptive wind noise:

Pretty cool territorial interaction between a Lesser Black-backed and a European Herring Gull – a Long Call duet at the start, then lots of Mew calls. A few chuckles and “how” calls from the Lesser Black-backed after it wins the fight.

Pair of Lesser Black-backeds Mew-calling in duet; some choking grunts while crouching on ground. Don’t miss Maarten van Kleinwee’s fascinating blog post about this pair and its behavior.

Feeding frenzy of birds, in Iceland in late May, being fed bread. All or mostly Lesser Black-backeds. Plenty of single-note calls.

Adult giving nasal “how” calls, with same from background birds

Alarm chuckles and a few decent mews; then a good long series of a duet of yelp calls; no head-tossing or other obvious displays; context uncertain. Near Reading, UK

Close-up of bird giving a few alarm chuckles. Alkmaar, Netherlands.

What Gulls Say

What Gulls Say

Have you heard an Ivory Gull vocalize? I have! (Didn't get any recordings, unfortunately.) Photo by Martha de Jong-Lantink, Spitsbergen, 8/19/2008 (CC 2.0).

Gull enthusiasts are weird.  They hang out at landfills.  They go to the beach when it’s freezing cold, or just to see what’s in the parking lot.  They’ll stare at a single bird for hours, puzzling over insanely minute details – the precise shade of gray on the back as measured by the Kodak gray scale, the age and condition of individual feathers, and even (I am not joking) the color of the inside of the bird’s mouth.  When it comes to identifying a mystery gull, they look at everything; they ignore nothing.

Except vocalizations.

Gulls have voices, but you’d hardly know it from reading the identification literature.

In all the thousands and thousands of words written each year about gull identification by experts on the ID-Frontiers listerv, vocalizations are mentioned approximately never.  P.J. Grant’s classic book Gulls: A Guide to Identification contains not a single mention of voice.  Howell & Dunn’s Gulls of the Americas refers to voice only in passing, in the introduction, and omits it from the species accounts. Olsen & Larsson’s authoritative Gulls of Europe, Asia and North America briefly mentions only a few sounds for each species.

I think the general neglect of voice can be explained by three factors:

  1. Gull sounds are variable.  Two individuals of the same species may sound very different.
  2. Gull sounds are plastic. Two calls from the same bird may sound very different.
  3. Gull sounds are poorly understood.

Those first two problems are not to be underestimated. Until recently, my main experience with gull sounds came from attempting to record some Ring-billed Gulls fighting over some bread I’d thrown them.  I was astonished (and frankly intimidated) by the huge variety of sounds I heard.  They whistled, they squealed, they barked, they bleated, they gargled:

I really couldn’t make sense of it.  Could these vastly different calls be merely variations on a simple-minded expression of hunger?  I began to worry that gull sounds might well be too variable to be of much use in identification.

Then I had another experience that changed my perspective.

The Western Gull Rosetta Stone

Long Call posture, held for most of the call after the initial bow. Herring Gull shown; Western is similar. From Tinbergen 1960a.

Last month I attended the Western Field Ornithologists’ Conference in Petaluma, California, where I tracked down local gull expert and field guide author Steve N. G. Howell for an answer to my burning question: “Where can I record gulls around here without too much ocean noise?”

After some thought, Steve sent me to the parking lot at Stinson Beach. It was just what I was looking for: an open, public area only a few yards from the ocean, but sheltered from the surf noise by a nice high earthen berm.  I got there early in the morning and found myself alone in the parking lot with a couple dozen gulls of two species (Heermann’s and Western).  Conditions were good, but even so, I was unprepared for the show.

It started when a pair of Western Gulls broke into a Long Call Duet.  Standing close together, they bowed their heads down once toward the pavement and then stretched their necks out at a 45-degree upward angle for the rest of the call:

Western Gull long call duet, Stinson Beach, CA, 9/29/2012.

Immediately, both birds transitioned into a slow series of long, rising wails, much like the sounds of a peacock, as they strutted around the parking lot in parallel, necks fully extended, bills pointed downward:

Western Gull "mew" duet, Stinson Beach, CA, 9/29/2012.

"Mew" duet posture. From Tinbergen 1960a.

Then one bird picked up some leaves and twigs in its bill.  It crouched down on the ground as though it wanted to begin building a nest scrape, or perhaps as though it were soliciting copulation. It began giving short, quiet grunts while its partner continued to wail occasionally:

Western Gull grunts during "choking" display, Stinson Beach, CA, 9/29/2012.

"Choking" display, from Tinbergen 1960b.

Just when I thought the show couldn’t get any better, a third Western Gull flew in, and one member of the duetting pair charged off to confront it.  The two locked bills in an intense tug-of-war, wings out for balance, giving a soft but threatening chuckle vocalization:

Western Gull alarm chuckle, Stinson Beach, CA, 9/29/2012.

Herring Gulls fighting, from Tinbergen 1960b.

Fans of Alfred Hitchcock may remember that chuckle — it’s the sound dubbed into The Birds whenever the Western Gulls gather ominously.  (Hitchcock added a little echo, to make it even spookier.)

When I got home, I discovered I’d recorded over half an hour of this remarkable show, and an additional ten minutes or more of myself narrating behavioral notes into the microphone.  It was the highlight of my entire trip to California.

Surprise, Surprise

The distinctiveness of each of the sounds I recorded, and the fact that each was obviously tied to a different social context, gave me a whole new view of gulls and their vocalizations.

Because I made those detailed notes on the posture and context of each sound, I was able to match each one up pretty well with the established literature on gull vocalizations (especially the pioneering work of Niko Tinbergen 1960a, 1960b).  The peacock-like wail is called the “Mew” call; the grunting accompanies the “Choking” display; and the chuckle is known as the alarm call.  Clearly, at least some of the time, gulls are more than just screaming kleptomaniacs.  They are capable of wonderfully complex and evocative social communication.

Flirting or Fighting?

My original hypothesis was that I was observing courtship behavior, but this may actually have been an aggressive territorial encounter, perhaps between two males. All of these displays are used in both aggression and in courtship.

Supporting the courtship hypothesis is the fact that this duetting pair never resorted to fighting.  When a third bird arrived, one of the displaying pair fought it off, while the other member of the pair looked on in agitation, giving a very long Long Call sequence.  When the third bird was driven off, the pair display resumed immediately between what I took to be the original two birds.

Furthermore, this pair’s strutting dance didn’t seem restricted to any territorial boundary. Instead it rambled over hundreds of yards of parking lot, seemingly at random.  Every once in a while the two birds would break off and drift apart, silently or with a few chuckle calls.  Once, when the two birds were widely separated, one of them crouched without apparent provocation and started giving a series of “Choking” grunts.  The second member of the pair immediately began walking towards it from a hundred yards away, taking up the wailing “Mew” cry when it got close.  The entire episode seemed to have the air of solicitation rather than confrontation.

Supporting the territorial interpretation, however, is the fact that it was late September.  Western Gulls aren’t supposed to start pairing up for mating until January at the earliest.  I couldn’t tell the sex of the birds. Although I kept expecting copulation to occur, it never did.  Nor did I see any of the unambiguous pair-bonding displays, such as the regurgitation of fish, which is the gull equivalent of recreational sex.

Gulls of several species have been reported to defend winter feeding territories, and that could have been what these birds were doing.  Perhaps a local breeder was fending off an interloper in search of winter turf.

The Take-Home Message

Somewhere near you, right about now, a pair of gulls is about to engage in a loud and conspicuous display.  They’ll do it wherever they find themselves — in a park, on a city street, at the grocery store — with little regard for what’s around them.  You’ll be able to walk right up to them with your camera, your smartphone, your recorder.

Do it.  Take notes on what you see.  Post your resulting pictures/video/audio to Flickr/YouTube/Xeno-Canto.  Then drop me a line.

We don’t know enough about gull displays, especially not in fall and winter.  Most research on gulls has taken place on the breeding grounds, and it’s possible that we don’t know about autumn courtship because we haven’t been paying attention.  We also don’t know much about identifying gulls by voice — but all we need to do is listen.  By sharing our observations online, we have the power to learn a ton.  Let’s give it a try.

The “Two-part Calls” of Empidonax

The “Two-part Calls” of Empidonax

If only it would sing! Probable Hammond's Flycatcher, Wyoming, 6/17/2010. Photo by Bryant Olsen (CC-by-nc-2.0)

Empidonax flycatchers are tough to identify by sight.  Every birder knows it.  They’re the classic bugaboo of North American bird identification.  That’s why every field guide mentions the importance of listening to their voices.

But Empids make a lot of sounds.  Forget about learning “the song” and “the call.”  Most Empids have repertoires of 6-8 different songs and calls. Some species, such as Pacific-slope and Cordilleran, have a dawn song that’s different from anything they say during the day.  Several, including Least, Yellow-bellied, Hammond’s, and Dusky, have complex, rarely-heard flight songs. The species with the largest vocabulary appears to be Acadian Flycatcher, which has all of the above types of song plus another type, sometimes called the “evening song,” which is the most complex of all.  (It may or may not be fully separate from the flight song.)

Today I’m going to be talking about a class of Empid vocalizations that don’t get much press. I’ll call them “Two-part Calls” since they don’t have an official name.  Based on their similarity, the “two-part calls” appear to be homologous — that is, evolutionarily equivalent, all descended from the same calling behavior of a common ancestor.

As far as I know, three species of Empids give these calls. In one species, the two-part call is familiar enough to be mentioned in field guides, at least. The two-part call of the second species is described only in the scientific literature.  And that of the third is, as far as I know, being described in this blog post for the first time.

Dusky Flycatcher: “Du-hic”

This call is mentioned in the Sibley Guide to Birds, Kenn Kaufmann’s Advanced Birding, and other well-researched field guides.  The “du” part of the call is nearly monotone, and the “hic” is shorter and slightly higher.  As you can hear in the following examples, the sequence is often more like “du, du, du, du, du-hic”.  Sometimes the “hic” notes will be given without a “du,” or after other “hics.”

This call may be given primarily by males, but I’m not certain of that. It’s given throughout the breeding season, but especially in long bouts at dawn and dusk during the early summer, prior to egg laying.

Hammond’s Flycatcher: “Peer-pewit”

Quite similar to Dusky’s “du-hic” but not mentioned in any field guides that I know, this call was first described in the scientific literature by James Sedgwick in 1975. Sedgwick called it the “k-lear whee-zee” call, but I think “peer-pewit” is a better transliteration. The “peer” note is slightly more downslurred than Dusky’s “du,” and the “pewit” is higher, longer, and much more distinctly two-syllabled than Dusky’s “hic.”  It’s given in similar situations to the “du-hic,” though it’s apparently  more likely to be heard later in the breeding season, after egg laying.

Yellow-bellied Flycatcher: “Whit-beert”

I stumbled across this vocalization in a good recording by Randy Little from Herkimer County, New York, which appears to be the only such recording in existence. The call is clearly related to the “du-hic” and “peer-pewit” of the western species, but instead of a drawn-out whistle, the first note is an emphatic “whit!” that resembles a more explosive version of the “whit” calls of other Empids. The second note is again an up-down-up trace on the spectrogram, rather like the Hammond’s “pewit” note.

Yellow-bellied Flycatcher "whit-beert" call, Woodhull Lake, New York, 5/30/1998. ML catalog #106901

(Click here to listen to the original recording on the Macaulay Library website.)

I cannot find any definite mention of the “whit-beert” call of Yellow-bellied Flycatcher in any published source.  The only possible reference I’ve found is this brief statement in the Birds of North America account:

One variation of Tu-Wee Call is of longer duration, described as thoo weep eh, thoo weep eh, or she weeps sir (Hausman 1946), or pea-wayk-pea-wayk (Dr. Hoy in Forbush 1927) and may actually represent call of different function.

That’s it.  Not much to go on.

So we’re left with more questions than answers.  Do other Empids give “two-part calls”?  What functions do they serve in each species?  Are they ever given by migrants?  Are they very rare in the Yellow-bellied Flycatcher, or merely under-reported?

I’d be interested to hear anybody else’s experience with this type of call in Empids.