Warbling Vireo is among the many widespread North American species with east/west vocal forms that meet on the Great Plains. Along with other examples of this type of song diversity (Marsh Wren, Blue-gray Gnatcatcher), eastern (gilvus group) and western (swainsonii group) Warbling Vireos may represent two species, and if they are ever split, song would be the best way to identify them.
Look at a range map of Warbling Vireo and you’ll see that it continues in a pretty much unbroken swathe across North America. The eastern and western song types meet at the Great Plains/Rocky Mountains interface, and in at least some of those both occur in a fairly close proximity but remain identifiable to type. For example, Warbling Vireos singing on the eastern plains of Colorado not far from the foothills are typically of the eastern type, while those from the foothills west are of the western type. In the Black Hills of South Dakota eastern types occur in the lower elevations, and are replaced by westerns in the higher ones (Birds of South Dakota). What is not very well studied, however, is whether there is a cline in song types anywhere in their range, and how the birds react to each others’ song types in areas in/near potential overlap.
The plumage of the two forms is extremely similar. Western is often cited as having a darker crown and more defined eyeline, giving it less of the “blank-eyed” look associated with Warbling Vireo. It is also a bit whiter on the underparts and darker on the back, and the bill is slightly thicker (Birds of North America). However, these differences are very subtle, not well studied, and hard to see in the field. A much more reliable way to separate the types is by their primary song, which has consistent (if not always obvious) difference. I’ll first talk about the eastern song type, which many readers should be familiar with it, and then contrast the western form.
The song of the eastern Warbling Vireos is what gave the bird its name. It is a pleasant caroling song that rolls along, often ending in an emphatic higher note, transcribed at times as “if I could see it I would seize it and squeeze it til it squirts” or some variation thereof. The song phrases are typically around 2.5 to 3.5s long, and are made up of a series rich whistles that are slightly modulated. In the song of eastern Warbling Vireo, most of the initial notes are near the same pitch, with a few higher notes thrown in towards the end of the song. Below are a couple of examples of eastern song:
Western Warbling Vireo songs differ from that of eastern mostly in terms of pitch. Most western songs tend to have more high pitched notes, and these are placed more evenly throughout the song, breaking up the rhythm so that the whole strophe sounds less sing-songy than the song of Eastern. While the song of eastern gives the impression of a series of low, caroling notes, the song of western gives a jumbled and less structured feel, with an overall higher pitch. This difference in sound takes a little bit of practice to pick out, and there are some birds (especially in the contact zone?) that are harder to place as one or the other. A couple of samples of the western song type:
Where from here?
Despite the fact that the songs of these two types of Warbling Vireo are fairly well differentiated, very little is known about what goes on in the contact zones. This is where just about any birder visiting the western Great Plains and eastern Rocky Mountains can make a difference. Pay attention to the Warbling Vireos! Are they eastern, western, undefinable? There are very few recordings available from these areas, so anything you find will be interesting and useful.
The Blue-gray Gnatcatcher sounds different in the West than it does in the East. As with geographic song differences in other birds, the differences in gnatcatcher songs might be of biological interest, perhaps encouraging the two groups not to mate with one another where their ranges meet. However, the differences in song are not well understood by most birders, nor particularly well described in most field guides. It doesn’t help matters at all that gnatcatchers are some of the most vocally complicated birds in North America. The longer one listens to them, the more confused one might get.
The Blue-gray Gnatcatcher is one of the very few North American birds whose western population has actually been better studied than the eastern population, at least when it comes to vocalizations. Most of what we know about the behavioral context of the different calls comes from a 1969 study by Richard Root that was conducted at the Hastings Natural History Reservation in Monterey County, California. Root’s observations suggest (and my own field experiences corroborate) that western Blue-gray Gnatcatchers have two basic kinds of song: a louder, simpler one used primarily in territorial advertisement, and a quieter, more complex one used primarily in close-range courtship. For today’s purposes, we’ll call them “simple song” and “complex song”.
Here’s the simple song of western populations, which Root called the “advertising song”:
This is one of those magnificent spectrograms that deserves a moment of silent admiration. The irregular spacing of the dark and light partials is not only visually striking, but a sure sign of polyphony, the simultaneous use of both sides of the bird’s syrinx, making for the distinctive whiny (some say “wiry”) tone quality of the gnatcatcher’s song. This type of song is characterized by short series of 3-7 similar-but-not-identical notes, each one of which is typically overslurred. A slight tendency toward up-and-down squiggling inside the individual notes on the spectrogram speaks to the slight burry quality of the sound.
This “simple song” comes in many variations across the western half of the Blue-gray Gnatcatcher’s range, even within the repertoire of a single bird, but the example above is quite typical. Compare it with the simple song of eastern birds:
We still see the irregular stripey pattern that signals polyphony, but now only two dark partials dominate instead of three or four, and those two darkest partials are at a higher frequency and farther apart from one another than the partials in western songs. This translates into a higher pitch with a thinner, less nasal tone quality. And the tendency toward burriness is typically more pronounced, adding a grating quality to many notes that western birds most often lack. Note shape also differs, with eastern birds showing much less tendency toward the rollicking up-and-down patterns of western birds, but this mark is highly variable in both populations.
Many people think of the complex song as the “true” song of gnatcatchers, probably because it better matches the traditional notion of a song as complicated and musical, but it is quieter and less frequent than simple song. Complex song is given by males in close-range courtship of females as well as some territorial boundary conflicts with other males. In both populations, the complex song is characterized by wildly diverse sounds, often including some mimicry, and herky-jerky rhythms that sometimes include a few repetitions of notes. The end result can sound something like a Brown Thrasher song played back at higher speed. But it’s usually easy to tell you’re listening to a gnatcatcher because of the liberal inclusion of individual whiny notes from the simple song. These notes, in fact, are the best way to tell whether you’re listening to the complex song of an eastern or a western gnatcatcher.
Note that there’s a complete range of intermediates between simple and complex songs in both eastern and western birds — the elements appear to mix freely, and a significant percentage of songs may be difficult to put into one category or the other.
The word “call” gets used a lot to describe the simple song, but gnatcatchers do have non-song calls. The calls are similar in quality to notes of the simple song, and they may integrade with it, so that it’s often difficult to tell calls and simple songs apart. But here are a few examples of what I think are true calls:
As far as I can tell, the shape of the call note is pretty constant between populations and individuals: a nice even downslur. The differences in pitch and tone quality of eastern and western birds exactly mirror the differences between the simple songs — eastern birds are higher-pitched and less nasal, and possibly less noisy as well.
Overall, the differences in voice between eastern and western Blue-gray Gnatcatchers are subtle, but consistent, and experienced field observers or those with recording equipment should be able to identify the two populations in the field by voice, even if they are out of range. The breeding ranges of the two populations may meet or even overlap in west-central Texas or part of Oklahoma. All the birds I recorded in the Texas hill country (Bandera and Kerr Counties) were clearly eastern birds, while the ones in Big Bend were clearly western, but I’m not clear on where the boundary is or whether intermediates occur along it. I would love to get more information if anybody can share it!
In my last post I promised a discussion of Fox Sparrow alarm and contact calls, and it’s time to deliver on that promise. Today we’ll look primarily at the calls most frequently heard from Fox Sparrows — the ones given in situations of mild alarm.
“Red” Fox Sparrow
The most common call of the Red Fox Sparrow group is a sharp “stack!” or “smack!” note that is often compared to the alarm calls of Brown Thrasher and Lincoln’s Sparrow:
“Sooty” Fox Sparrow
The common call of the Sooty group is virtually identical to that of the Red group, and individual calls are probably indistinguishable in the field or on the spectrogram. Sooties may tend to call at a faster rate, but it could be that the birds below are simply more agitated:
“Slate-colored” Fox Sparrow
The Slate-colored’s most common call is similar to those of the Red and Sooty groups, but lasts about 50% longer on average, giving it a slightly squeakier quality, somewhat reminiscent of the tennis-shoes-on-a-gym-floor sound of Black-headed Grosbeak’s call, but downslurred instead of upslurred:
The Borror Lab has another excellent online example from Utah. The difference between Slate-colored calls and those of the two prior groups is quite subtle, but distinctive in these examples. There remains some doubt as to whether all Slate-coloreds sound this way, or only the ones in Colorado and Utah. This recording from Washington is labeled as a Slate-colored but sounds more typical of the Sooty group.
“Thick-billed” Fox Sparrow
The call of the Thick-billed group is very unlike the above calls, both spectrographically and to the ear. Often compared with the calls of California Towhee and White-crowned Sparrow, it is a high-pitched, musical “tink” note:
Listen to other examples online at the Borror Lab  and the Macaulay Library .
Agitated “tsip” calls
Identifying a Thick-billed Fox Sparrow by call would be a cinch, but for one inconvenient fact: Fox Sparrows of all four groups make high-pitched repeated “tsip” notes when agitated. Here are some agitated “tsips” from a Slate-colored Fox Sparrow:
Joseph Blacquiere recorded these “tsip” notes from Red Fox Sparrows during his 1979 master’s thesis work, and the Macaulay Library has a recording of similar notes from a Thick-billed Fox Sparrow on a still-undigitized recording. It’s highly likely that Sooty Fox Sparrows also give these calls. The Slate-colored bird that I recorded mixed these “tsips” with the standard alarm calls during its initial excited reponse to playback of its own song, before beginning to respond with song strophes. Blacquiere heard the “tsip” calls from Red Fox Sparrows on fewer than 10 occasions, always from males in extreme agitation.
The “tsip” calls are spectrographically distinct from the “tink” calls of Thick-billed Fox Sparrows, but can be quite difficult to distinguish by ear. Some caution is therefore warranted when identifying Thick-billed Fox Sparrows by their “tink” calls — other Fox Sparrows can sound similar when agitated.
It’s late October — for many birders in the eastern United States and along the west coast, time for the Fox Sparrows to arrive from the north.
What arrives from the north, however, could be a bright rufous-red finch-like fellow, a slaty-gray and brown bird, or a dark chocolate-colored skulker, depending on what part of the country you’re in. These different-looking populations have been considered merely well-marked forms of a single species, Fox Sparrow (Passerella iliaca), at least as far back as Harry Swarth’s (1920) treatise, and the current generation of taxonomists, dominated by “splitters,” has so far left the species intact.
But several recent genetic studies (most notably Zink and Weckstein 2003) have provided evidence that four groups of Fox Sparrows have separate evolutionary histories and may deserve species rank:
Red Fox Sparrow (iliaca/zaboria group), the brightest form, with strong reddish highlights in the wings, tail, back, and head, and strong reddish streaking below;
Slate-colored Fox Sparrow (schistacea group), a high-elevation breeder with some rusty in the wings and tail, but otherwise primarily slate-gray, with little patterning on the head;
Sooty Fox Sparrow (unalaschensis group), the darkest form, with little patterning on the head or wings;
Thick-billed Fox Sparrow (megarhyncha group), which resembles the Slate-colored in plumage but, at least in the southern half of its range, sports a significantly bigger bill.
A 2000 paper in Birding by Kimball Garrett, Jon Dunn, and Robert Righter pointed out some differences in call notes between the groups that could have bearing on their identification and taxonomy. Although Don Roberson has created an invaluable in-depth online guide to visual identification of Fox Sparrow groups, I don’t know of any similarly comprehensive treatment of the calls — and so I figured it was time to treat this topic on Earbirding.
Among the many things that Fox Sparrow say are three major classes of calls: flight calls, alarm/position notes, and high-agitation “tsip” calls. We’ll start today with the flight calls and cover the others in a future post.
The “flight call” of the Fox Sparrow is in fact often given by perched birds; it may indicate mild alarm, and it may sometimes be given as a contact call. It is typically a high-pitched, strongly underslurred, polyphonic “seet” or “suweet,” similar to the flight calls of Song and White-throated Sparrows (see this page by Paul Driver for more info on separating flight calls of sparrows from one another). The gurus on the flight call listserv often refer to “Song/Fox” sparrow flight calls, as the two can be difficult to tell apart in many cases.
All populations of Fox Sparrow give flight calls that are basically similar, but in my attempts to find examples from each population, I have turned up some interesting potential differences. Here is a side-by-side spectrographic comparison of flight call examples from across the continent:
All these examples can be heard online, but to make the composite spectrogram above I had to cull flight calls from the middle of many recordings I don’t have permission to remix, and some of the flight calls that appear right next to one another actually occur several minutes apart on these recordings, with other calls or songs in between.
Call 6: Slate-colored Fox Sparrow flight call, Utah County, UT, 4/1/2000, Borror Lab #30600
Calls 7-8: Slate-colored Fox Sparrow flight calls, Pierce County, WA, 9/22/2009, Xeno-Canto #39269
Calls 9-12: Fox Sparrow flight calls from a bird matching the “Canadian Rockies” illustration in the Sibley Guide to Birds, Yuma County, CO, 12/28/2008. Recording by me; see also photos of this individual  courtesy of Bill Schmoker.
Calls 13-14: Red Fox Sparrow flight calls, Osage County, OK, 3/21/2008. Recording by me.
Calls 15-17: Red Fox Sparrow flight calls, Huntingdon Valley, PA, 11/1/2010, Xeno-Canto #69940.
Although I’ve placed them in the “Slate-colored” group per the recordist’s notes, I think it’s possible that calls 7-8 may actually pertain to the “Sooty” group — they are from the west side of the central Washington Cascades in late September, where Sooty is probably the more likely bird. In addition, both these two flight calls and the contact/alarm calls on the same recording are a closer match for other examples of Sooty Fox Sparrow than they are to calls of Slate-colored (more on contact/alarm calls next time).
If the Washington bird is indeed a Sooty, then the flight calls in the figure above would appear to fall into three similar but somewhat distinct groups:
Sooty group (1, 7 & 8): High-pitched and deeply underslurred, with a strongly U-shaped trace on the spectrogram; note that the Oregon bird is giving the only single-voiced (not polyphonic) call of the bunch;
Thick-billed/Slate-colored group (2-6): Lower-pitched, more shallowly underslurred, with a spectrogram like an open-mouthed smile;
“Canadian Rockies”/Red group (9-17): High-pitched, strongly polyphonic, slightly burrier than other flight calls, and more strongly upslurred — note the tendency towards a “Nike swoosh” shape on the spectrogram.
If the Washington bird is a Slate-colored after all, then the deep U-shape may not be as distinctive a characteristic of the group as are the polyphony and the low pitch; if that’s the case and the above call by the Oregon bird is representative of Sooty Fox Sparrows everywhere, then Sooty may be the only group without a polyphonic flight call.
Overall, this is a pretty small sample size to make generalizations about, so if anyone can point me toward more examples of Fox Sparrow flight calls, particularly from the western groups, I’d love to see if the apparent patterns may hold. I’d also be glad of comments on the identification of the “Canadian Rockies” bird — it’s physically a pretty good match for the illustration in Sibley, but birds breeding in the Canadian Rockies should by all accounts fall into the Slate-colored group rather than the Red group. Why its flight calls appear to more closely resemble those of the Red Fox Sparrow group is not entirely clear.
Over the entrance to that “intellectual space” in which researchers debate taxonomic limits in the genus Junco, there stands a gate bearing an inscription in fourteenth-century Tuscan:
LASCIATE OGNI SPERANZA VOI CH’INTRATE
Just as Virgil guided Dante through the Inferno, I wish that I could offer you safe passage through the many circles of biological complexity centered on the single hellish question of how many junco species there really are. But there’s no such thing as safe passage. There’s no getting around it: the juncos are devilishly complicated.
Most birders in North America focus on telling the different junco forms apart by sight, which is appropriate, since most North American juncos sing a single high-pitched musical trill that is pretty much the same whether it comes from a Slate-colored, a Pink-sided, an Oregon, or a Gray-headed Junco:
A few of the Dark-eyed Juncos in all of these populations will occasionally sing a slightly more complicated two-parted trill:
And some of the Gray-headed Juncos in the southern Rocky Mountains will sometimes end with a slight flourish of 1-2 different notes:
As one moves farther south in the mountains, the junco songs become gradually more complicated. The “Red-backed” Juncos of northern Arizona sing significantly slower and more frequently two-parted songs than the Gray-headed Juncos they closely resemble:
By the time you reach southern Arizona, the juncos’ eyes have turned yellow, virtually all of their songs have become 2- or 3-parted, the trills have slowed, and terminal flourishes have become common:
Farther south, in central Mexico, the songs get even more complex, with fewer repeated notes, but they don’t last quite as long:
The southward trend towards brevity and complexity continues all the way down to the isolated, fireproof Volcano Junco of Costa Rica and Panama:
“Baird’s” Junco, an outlier
At least one isolated Junco population doesn’t really fit the pattern we’ve just described. At the southern tip of Baja California, high up in the Laguna mountains, one finds birds named after Spencer Baird that closely resemble the Yellow-eyed Juncos of adjacent mainland Mexico, except slightly paler, with a light brown back and soft pinkish flanks. Oh, and they happen to sing an extremely complex song:
Anyone who has ventured into the Sierra La Laguna knows that the endemic Baird’s Junco, currently considered a subspecies of the Yellow-eyed Junco by the AOU, doesn’t sound a bit like most other members of its genus. When we first heard it on the WFO/SJV expedition in 2008, some in our group looked around for a Passerina bunting; I thought I might be hearing a Rufous-crowned Sparrow. Howell and Webb (1995) say the song suggests a small Troglodytes wren, and split the species from Yellow-eyed in large part on that basis.
I recorded enough Baird’s Junco song in Baja California in 2008 for a formal analysis, but I didn’t have the statistical skills to pull it off by myself, so I collaborated with Clint Francis, who was then a graduate student in Alex Cruz’s lab here at the University of Colorado in Boulder, to try to figure out whether Baird’s song was really as different from the songs of mainland juncos as it seemed to the human ear. We wanted to know whether the more complex junco songs from central and southern Mexico might show an intermediate syntax linking the very different-sounding Baja and Arizona populations.
Our results, published this month in the Wilson Journal of Ornithology (subscription required), show that Baird’s sings quite differently than mainland juncos. Figure 1 from our paper illustrates this quite nicely:
Baird’s Juncos virtually never repeat a note or phrase, and they use far more unique notes and phrases than either Oaxaca or Arizona birds. In these features, the values for Baird’s didn’t even overlap with the values for mainland birds. A discriminant function analysis of 12 features easily distinguished Baird’s from mainland birds, but did not easily distinguish between Oaxaca and Arizona songs.
What does this mean? On the whole, it means that human ears don’t lie: Baird’s Juncos really do sing a highly differentiated song. It is quite possible that this song would reproductively isolate them in the unlikely event that they came into contact with mainland populations, meaning that Baird’s Junco may deserve full species status. We stopped short of recommending a split in our paper until playback experiments and/or genetic analyses can be done. However, a few years from now, Baird’s Junco (Junco bairdi) might just take its place on the AOU checklist as the next new North American Junco species.
The neotropics are blessed with many families of birds that you can’t see in your neighborhood park up north. But perhaps none of these are more interesting, from an acoustical perspective, than manakins. They defy expectations when it comes to making sounds: some of them rub modified feathers together like a cricket, while others beat at the air, snap their wings against their body, or engage in elaborate, ritualized displays involving multiple birds making a smorgasbord of weird mechanical sounds. And some of them just sit there all day on one perch and say “nicky-the-greek” over and over and over again.
Being suboscines, manakins are thought to not learn their songs , instead having them hard-wired into their DNA. And as with other suboscines, this has important implications for their taxonomy when major differences between populations occur. In at least one manakin clade (White-ruffed and White-bibbed Manakins), differences in vocalizations and displays played a role in considering them separate species.
When it comes to sounds, the White-crowned Manakin (Pipra pipra) isn’t the most interesting of the family. Its displays are mundane compared to those of, say, Long-tailed Manakin. And the mechanical sounds it makes are limited and mostly simple. But it does appear to have a plethora of distinct vocal types that may well correspond to different species, despite the fact that they all look nearly or completely identical to each other in plumage.
A recent trip to the remote Cordillera del Condor in far southeastern Ecuador piqued my interest in this vocal variety when I heard a new vocal type, one I hadn’t even known existed until the day before. That brought the total vocal types that I knew of up to three, each replacing the other in very close proximity in a complex system of allopatry that is unlike any other species group in Ecuador. I was interested to see how many there really were if I listened to recordings from throughout their range. What I found shows that there are more to learn about manakins than just how they make their weird noises (which is what most recent manakin research has focused on)…complex taxonomical puzzles also remain to sweeten the pot. I’ve written a feature on xeno-canto detailing what I’ve found – take a look!
Guest post today by Walter Szeliga, who is starting to turn his audio recorder on some very interesting problems of identification and taxonomy.
The specific status of the Sage Sparrow in North America has been in question since the publication of Ridgway’s 1887 treatise A Manual of North American Birds. In that volume, he attaches a footnote to the entry for Amphispiza belli nevadensis (p. 427): “With scarcely any doubt a distinct species”. Further subspecific division of the Sage Sparrow occurred in 1905 with Grinnell’s publication of “The California Sage Sparrow,” in which he described a third subspecies, “Intermediate Bell Sparrow,” A. b. canescens (Latin for “turning gray”). In addition to these three subspecies, a fourth, A. b. clementeae (“San Clemente Sage Sparrow”) is endemic to San Clemente Island — which, as a live firing range for the Navy, is all but impossible for most people to visit.
Recently, modern techniques, such as genetic sequencing (Cicero and Johnson 2007), have suggested that Ridgway’s feeling may be correct. Furthermore, a recent article in Zootaxa (Klicka and Banks, 2011) essentially constitutes a formal proposal to elevate A. b. belli and A. b. nevadensis to species status, complete with a new generic name, Artemesiospiza.
However, whether A. b. canescens should be recognized as a species distinct from A. b. belli remains in question. For now, Klicka and Banks (2011) lump it in with A. b. belli. Were the Sage Sparrows to be split, more birders would surely wish to identify these different groups in the field.
But identifying these groups in the field is tricky. During the breeding season, there are only a few regions of the American West where Sage Sparrow subspecies come in contact — a small area near Bishop, California, where canescens meets nevadensis; and a thin strip of the eastern California Coast Range from near Parkfield southward to the Little San Bernardino Mountains, along which belli meets canescens. In this area belli and canescens prefer quite distinct habitats, canescens breeding in the saltbush (Atriplex sp.) found on the floor of the Mojave Desert and belli preferring mountain chaparral dominated by chamise (Adenostoma sp.).
While Sage Sparrows on breeding territories can largely be identified to subspecies by range and habitat, the situation is quite different during migration and winter. The nominate A. b. belli, “Bell’s Sparrow,” is primarily restricted to the Coast Ranges of California and Baja California and is mostly sedentary, but its territory is invaded each winter by members of both canescens and nevadensis. In fact, these “winter” invasions begin very early for some canescens, which disperse after breeding to higher elevations in the range of belli as early as June (see Cicero 2010).
Thus, vocal and visual differences are frequently required to separate the three mainland Sage Sparrows to subspecies. Fortunately, there are some plumage differences that could prove useful in the field.
A. b. belli lacks distinct streaking on the mantle, while A. b. nevadensis shows streaking on the mantle.
A. b. belli has a distinct black malar stripe, while A. b. nevadensis shows a less prominent pale gray malar stripe.
A. b. belli shows a greater contrast between the head and body, with a darker gray head contrasting with a brownish body, while nevadensis is paler overall, with less contrast.
In the hand, nevadensis is a distinctly larger and longer-winged bird than belli, features consistent with the greater migratory distance of nevadensis. Unfortunately, size differences are all but useless under field conditions.
Notice that all of the field marks mentioned so far involve separating A. b. belli from A. b. nevadensis. In nearly all of the categories mentioned above, A. b. canescens show features intermediate between belli and nevadensis; hence Grinnell’s suggested common name of “Intermediate Sage Sparrow”. For good comparative photos of all three subspecies, check out Robert Royce’s photo galleries of belli, canescens, and nevadensis.
That brings us to vocalizations.
“Bell’s” Sage Sparrow (Amphispiza belli belli)
First, let’s look at a song from A. b. belli. A cursory glance at the spectrogram reveals a complex jumble of upslurred and downslurred notes on different pitches, for the most part lacking trills or buzzes of any significant length. As in other Sage Sparrows, songs from individual birds tend to be highly stereotyped, with most birds singing only one songtype and rarely giving shorter incomplete versions of this songtype.
Moving on to A. b. nevadensis, we immediately notice a difference. The spectrograms show prominent trills or buzzy notes, most of which cover a fairly broad frequency range. The cadence of the song is different, the mix of quick short notes and longer buzzes giving it a stop-and-go, herky-jerky rhythm. Note the tendency for the ending to recapitulate the first part of the song, a tendency shared by many males in every subspecies group.
Here’s another nevadensis Sage Sparrow from Dolores County, Colorado:
And here’s a gallery of Xeno-Canto uploads of this subspecies:
A typical nevadensis song is fairly easily distinguished fromclassic examples of belli by its lower pitch, richer burry texture thanks to the trilled notes, and more syncopated rhythm. However, note that a few nevadensis songs, like Tayler Brooks’ recording at lower left, seem approach those of belli in these characteristics and might be difficult to identify in the field in the absence of other clues.
Interestingly, analysis of song length, and number of notes per song suggest that A. b. nevadensis has the longest song (~2.1 seconds, 8 notes per second), contrary to the suggestion in the Sibley Guide. In fairness though, individuals from A. b. belli do sing more notes per second (12 notes per second, ~1.4 seconds per song) than A. b. nevadensis. This does give the impression that they are singing a longer song.
Not only is canescens intermediate between belli and nevadensis in range and appearance, it also appears confusingly intermediate in song. Some songs, like the three below, closely resemble those of belli:
Other recordings of canescens from farther north and east appear more similar to nevadensis song:
Here are a couple of recordings from within the breeding range of canescens in January and March, when migrant nevadensis can’t be ruled out:
While range, habitat and plumage may help identify many Sage Sparrow individuals to subspecies, there also appear to be useful differences in song. These song differences appear to be greatest between A. b. nevadensis and A. b. belli, with A. b. canescens forming a confusing intermediate group. It’s possible that song in canescens grades clinally from nevadensis-like songs in the northeastern part of its range to belli-like songs in the south and west. It’s equally possible that some of the nevadensis-like songs above actually belong to that subspecies instead of canescens.
On the whole, it seems that “classic” songs of nevadensis and belli are fairly easy to distinguish, but any Sage Sparrow singing an intermediate song may not be identifiable to subspecies by voice alone.
In 1989, the American Ornithologists’ Union split the Western Flycatcher into two species: Pacific-slope Flycatcher (Empidonax difficilis) and Cordilleran Flycatcher (Empidonax occidentalis), on the basis of vocal differences, differences in allozyme frequencies, and an area of sympatry in the Siskiyou region of northern California, where they were reported to mate assortatively.
Ever since then, these two species have been causing headaches for birders all across western North America. The conventional wisdom is that they are impossible to identify by plumage or structure, even in the hand. Voice is the only field mark.
Male position note
Most birders use only one clue to identify these two species: the subtle but distinct difference in the position notes of the males. Pacific-slope gives a one-syllabled upslurred whistle, and Cordilleran gives a two-syllabled upslurred whistle:
In “classic” examples like those above, note the distinct kink near the beginning of the Pacific-slope call, and the distinct break in the Cordilleran call (which can sometimes be rather indistinct, as it is in the second call on the right-hand spectrogram above).
However, the situation with these call notes is quite messy. For one thing, the calls are frequently variable within individual males, as in these examples:
Some of the Pacific-slope examples above sound vaguely two-syllabled, and some of the Cordilleran examples sound distinctly one-syllabled. Here’s a more extreme version of the monosyllabic call type from a Cordilleran on territory in Colorado:
Note the lack of the distinct kink on the spectrogram that is typical of Pacific-slope. That kink, however, makes little difference to the human ear, and birds that sound like this are likely to be identified as Pacific-slopes in the field.
I believe that’s what happened yesterday when a potential first state record Pacific-slope Flycatcher was reported yesterday in Gregory Canyon, here in Boulder, Colorado. I went to record the bird this morning, and captured a few of its calls on tape:
Less well-known than the differences in position note are the differences in the male’s dawn song, which is usually given only before the sun rises. As with the position notes, the differences in dawn song are subtle and subject to both individual and regional variation.
Like the songs of Dusky and Hammond’s Flycatchers, the dawn songs of Pacific-slope and Cordilleran Flycatchers consist of three different phrases usually repeated in an “ABC” pattern:
Compare each note of the songs:
In both species, the first element of the dawn song is a brief, high-pitched, simple whistle of variable inflection.
The second element is the loudest, longest, and most distinctive: in Pacific-slope it usually sounds vaguely two-parted (or at least split in the middle by a consonant), whereas in Cordilleran it usually sounds like a single slurred whistle. (Thus, the distinction in this case is the reverse of that in the position notes.)
In both species, the third song element is a clipped, lower-pitched, two-syllabled note; the second note tends to be higher than the first in Pacific-slope and vice versa in Cordilleran, but this difference is somewhat variable.
When I originally recorded the putative Pacific-slope Flycatcher in Gregory Canyon this morning, I thought I was hearing the standard Cordilleran dawn song from it in addition to its Pacific-slope-like position note. Upon examining the spectrograms of my recordings, however, it became clear that the bird singing the dawn song and the bird giving the position note were different individuals, since their vocalizations overlapped a number of times on the spectrogram. Thus, I do not believe that I heard dawn song from the Gregory Canyon bird this morning. However, I believe it can still be identified as a Cordilleran given the shape of its position note. Furthermore, I heard Cordilleran dawn song and Pacific-slope-like position notes from another individual male about half a mile farther up the canyon this morning.
On the whole, these two species, if they are indeed species, are exceedingly difficult to identify by ear. Spectrograms of the dawn songs or male position notes should be identifiable, however. Thus, decent recordings would be essential to document any occurrence of either species outside its normal breeding range.
Andrew Rush and Arch McCallum are currently researching these birds in great detail, so hopefully we will know much more about taxonomy and identification of “Western” Flycatchers in the next couple of years.
The Northern Pygmy-Owl is a fascinating bird for those of us interested in vocalizations and taxonomy. Many people think that what we call “Northern Pygmy-Owl” may contain somewhere between two and four species, based on regional differences in vocalizations. Here’s a brief overview of the differences, according to The Sibley Guide to Birds (2000), with a typical spectrogram and sound of each:
According to Sibley, birds along the Pacific Coast of North America “give very slow single toots (1 note every 2 or more sec).” The example below is even slower than most; 2.5 seconds between notes seems pretty standard. Although one might expect birds in Montana to be part of the Interior West group, the sole recording available seems to fit better in this group.
Interior West group
Very few recordings of this group are available online (or anywhere else) — just two or three from Colorado  and one from Utah. They all seem to give single notes at very regular intervals, just over 1 second apart, totalling about 50 “toots” per minute when they’re going full-bore.
Mexican group (“Mountain” Pygmy-Owl)
Sibley says these birds “give mainly paired notes more rapidly (about 1 pair every sec).” Paired and single notes are usually mixed together, as on the recording below, and the paired notes are only slightly closer together than the single ones:
However, “Mountain” Pygmy-Owls also sometimes forgo the paired notes in favor of a rapid-fire string of single hoots almost identical to the song of the Northern Saw-whet Owl:
What we don’t know
Nobody knows exactly where the changes between these songtypes occur, or how abrupt they are, because we just don’t have enough data. Most recordings of Northern Pygmy-Owl are of the highly vocal Mexican birds. As I mentioned above, very few recordings exist of the Interior West birds. There are none from potential areas of transition, like Idaho, Wyoming, northern Arizona, or New Mexico.
Now, my friend Arch McCallum is setting out to get to the bottom of this tricky situation — and you can help.
If you have access to Northern Pygmy-owls anywhere in their range this spring and summer, please do one of the following:
Find a singing pygmy-owl.
Get out a stopwatch and count how many “toots” the bird makes in one minute.
Send this information, along with location, date, and time of day, in an email to Arch (mccalluma AT appliedbioacoustics.com) or post it in the comments below.
If you wish, you can also make a one-minute audio recording. (Just take a video with your digital camera, or get a cheap voice recorder if you don’t already have the means.) Actually, if you wish, you’re welcome to record (or listen to) the bird for longer than a minute! The more data, the better.
Hope to see a lot of data points roll in this spring! Here’s to good owling.
Anyone who has birded much in South America will be familiar with what I like to call “field guide taxonomy”. Many authors of South American field guides often make taxonomic decisions not yet accepted by “official” checklists such as the SACC, Clements, or the IOC. Often these are splits and lumps that are obvious and will doubtless be supported with future research, but just as often they are made with very little information justifying the split.
One such split is that of Buffy Tuftedcheek in Ridgley & Greenfield’s Birds of Ecuador. They support their split soley on range and plumage, and don’t even mention vocalizations: “P. johnsoni (Pacific Tuftedcheek) of western Colombia and western Ecuador is regarded as a monotypic species separate from P. lawrencii (Buffy Tuftedcheek) of Costa Rica and western Panama, based on its very different distribution and distinct plumage differences.”
Recently, on a trip to Costa Rica, I was able to record the song of nominate Buffy Tuftedcheek. Since I had been unable to find any cuts of this vocalization prior to my trip, I was completely unprepared for how different it sounded from Pacific Tuftedcheek (which I am very familiar with from living in Ecuador). I’ve posted a few cuts I got in Costa Rica on xeno-canto, and written a feature comparing them with both Pacific and Streaked Tuftedcheek (which some people consider conspecific with Buffy Tuftedcheek, and which sounds far more like nominate Buffy than either one sounds like Pacific).
During the course of my research, I also stumbled upon some interesting variation in the songs of the widespread Streaked Tuftedcheek. Unfortunately there are far too few samples to get a handle on this variation, but I’m just itching to get my hands on some more cuts to see what is really going on… You can read all about it here.
Finally, if any of you have ANY recordings of any tuftedcheeks, I would encourage you to upload them…sample sizes are depressingly small at the moment.