Canyon Wren, Irish Canyon, Moffat County, Colorado. Photo by Andrew Spencer

It’s a commonly held conception that only male birds sing.  And for many birds in North America that is indeed the case.  However, there are cases of female birds that sing as well – finches, orioles, cardinals, and some warblers (occasionally), among others.  In North American wrens, for the most part, only the males sing, but  exceptions include House Wren, Cactus Wren, AND Canyon Wren.

This is in sharp contrast to tropical wrens, who have among the best female singers in the entire avian world.  Indeed, the duets of some of the South American wrens are probably some of the all time great bird sounds on the planet!  Take a listen to these two different subspecies of Plain-tailed Wren: XC42098 and XC58882.

Back up here in North America, the song of male Canyon Wren is among the best known (and most beautiful) of the sounds in the west, echoing off canyon walls just about anywhere with appropriate habitat – take a listen below.

But Birds of North America gives an interesting tidbit if you dig a bit further: “Both sexes sing, but female song is rarer and usually shorter.”  It goes on to describe a couple of female vocalizations, but without spectrograms and without a whole lot of detail.  So it is up to the observer to figure out what female song is when in the field.  A while back Nathan told me about this vocalization, and gave me a recording he made in Arizona that he thought was the female song, asking me to keep an ear out for it and to try to get a better recording.  I was intrigued – there’s little I love more than a bird sound mystery – so I edited the recording for playback and put it onto my i-pod (you can also hear another example at 46 seconds on LNS#21482).

A few weeks later I had my first chance.  I was in Irish Canyon in far northwestern Colorado, and I heard the liquid notes of a Canyon Wren song on a nearby cliff.  I walked over, and played the tape in the middle of the bird singing.  I was a bit startled at what happened next – the singing bird stopped, mid-strophe, and flew right in at me, calling loudly and angrily.  It was also giving an unusual call type (see below), and continued giving it for some time, from the middle of pinyon pine trees and on the ground.  Eventually it flew up to the top of a tree and started singing again, but still reacted the same way the next time I played Nathan’s recording. What it did not do, nor did any other bird in the area do, was sing the “female” song that I had on my i-pod.

I took this as something of a challenge.  That morning I played to three more singing Canyon Wrens.  All reacted to the track, though none as strongly as the first bird, but none responded with the same vocalization as the one on the tape.

Finally, about a week later, I hit pay dirt.  This time I was down near the town of Dinosaur, and I randomly played Nathan’s cut just to see what would happen.  I didn’t hear a response, and after waiting a couple of minutes I began to walk away.  Then there it was!  High up on the cliff was a perfect carbon copy of what I had just played.  I got a witness recording, and began to move in.  I was soon watching the bird as it sang from on top of prominent rocks, and after another quick playback, on some nearby tall shrubs.  To hear for yourself what it sounds like, take a listen to the cut below:

When I played the recording I had gotten to the bird in question it would react immediately and aggressively, flying in very close and giving the same vocalization back.  Interestingly, when I played back the normal song, it would barely react, at most just sitting up and looking around briefly.  Frustratingly, I was unable to ever confirm two birds at once, so I can’t say for sure that this is from a female bird.  However, about half an hour later there was a bird in the same territory singing the normal song, and when I played back the “female” song to that individual it didn’t react much at all, and the one time it did it came in low giving the same calls as the bird from Irish Canyon.  When I played the normal song back to it, though, it went ballistic, flying right in and singing at close range.

I also took photos of both birds, and examining these later I could see what I believe are differences between the two.  SO there seems to be a preponderance of evidence for there being two birds in the same territory.  And since one of those birds was singing normal song and acting in a territorial manner (and is thus, presumably, a male), it would stand to reason that the bird I recorded singing “female” song was, in fact a female.  But I can’t be certain, so I guess I’ll have to keep trying!

Warbling Vireo, Illinois, 8/18/2010 by Ken Schneider (CC 3.0)

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.

Warbling Vireo range map by Nathan Pieplow

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.

Eastern:

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:

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.

Singing White-winged Dove, Monterrey, Mexico, 4/11/2010. Photo by Ereenegee (CC 3.0).

I love an auditory mystery.

For many people, an avian auditory mystery is a “whodunit” — a quest to find out what species of bird is singing.  But my favorite mysteries are “why-dunits.”  These are puzzles solved not by the identity of the singer, but by the meaning of the sound.

Major why-dunits are more common than you might think.  Let me put it this way: it’s difficult to take your camera to a local park and capture a bird plumage or behavior that has never before been photographed.  But it’s about twenty times easier to make an audio recording of a call or behavior that has never before been audio recorded.  And finding out what kind of sound you’ve recorded takes real detective work.

This is a dove detective story.  A White-winged Dove detective story, to be precise.

Just the facts

Unlike any other dove species in North America, White-winged Doves regularly alternate two different songs, a long one and a short one.  The long one goes on for up to 10 seconds or so, ending with a distinctive sequence of alternating downward and upward voice breaks:

White-winged Dove long song, Sierra County, NM, 2/24/2008.

The short song is the four-note “who cooks for you?” phrase familiar to many people in the arid Southwest.  Note the long, breathy introductory syllable, which is only audible at close range (this will be important later):

White-winged Dove short song, Sierra County, NM, 2/24/2008.

That’s what White-winged Doves should say, according to the field guides.

The Strange Case of the Two-note Song

Where were you on the morning of May 16, 2009?  I was in Guadalupe Canyon, Arizona, a few hundred yards from Mexico, recording a dove sound unlike any I’d ever heard, an odd two-note phrase with the second half burry:

Unusual White-winged Dove song, Cochise County, AZ, 5/16/2009.

Like any good gumshoe, I first eliminated the usual suspects.  It wasn’t the usual song of the Mourning Dove (3-5 notes), Eurasian Collared-Dove (3 notes), Rock Pigeon (1 note), or Common Ground-Dove (1 note).  Inca Doves sing two notes, but this wasn’t like the typical song or even the courtship song of that species either.  I wondered briefly if it could be some rare vagrant from south of the border — Ruddy Ground-Dove, or perhaps Arizona’s first Red-billed Pigeon or White-tipped Dove — but no, I knew those songs and they sounded nothing like this.

The most likely scenario, then, was that I was hearing an uncommon vocalization type from a common bird.   Most dove species in North America have multiple vocalizations, named by ornithologists for their function — an “advertising coo” to catch the ladies’ attention; a “display coo” to get them out onto the dance floor; a “nest coo” to entice them home to the bachelor pad.  The “nest coos” in particular can sound quite different than the typical songs, and they are poorly represented in audio recordings.  Was this a new “nest coo” for my audio collection?

Whatever the two-note dove was, it seemed to be countersinging with a White-winged Dove giving the typical short song.  There were definitely two birds, because occasionally they would vocalize at the same time, but I could only see one White-winged Dove, and I couldn’t be sure whether it was making the typical song or the odd one.  When it flew away, both songs ceased.

Searching for Clues

I went to the Birds of North America account for White-winged Dove to see if the two-note song had been described.  But this only increased my confusion.  The account clearly described the long song and the short song as different forms of the “Advertising Coo,” but its description of the “Nest Coo” was also apparently a description of the short song:

“Nest” call apparently very similar, consisting of 5 syllables, 3 in first half and 2 in second half, a single growling note (first syllable) followed by 2 barking notes (second and third syllables) connected together and with rising emphasis in second bark, then 2 barking notes together with a falling inflection and last one somewhat prolonged ( Whitman 1919, Goodwin 1983).

The five-syllable “nest call” starting with a “growling note” is pretty clearly just the short song heard at close range.

There was no mention of two-noted calls or burry notes anywhere in the article.  I had to consign my weird recording from Arizona to the “unsolved mysteries” file until more information came along.

Reopening a cold case

In Mexico in 2010, I wandered for two weeks among courting White-winged Doves.  I didn’t hear or record the two-note song again, but I did find some clues that began unraveling the mystery.

For one thing, I witnessed courtship displays of White-winged Doves for the first time, as described in the BNA account:

Male perches on sturdy twig or branch while female rests nearby, watching behavior. Male lowers body forward, head almost below level of perch, raises wings straight up and over body, lifts and fans tail, and rocks backward to normal perching position.

What the BNA account barely mentions is that the male gives the short song as part of this display.  From the vocal notes on one of my recordings:

He’s sticking his wings out at a 45 degree angle above his body and a little bit in front of his body.  They go up at the very beginning of his call, during that first note.  They come down slightly emphatically right at the beginning of his second note, at the beginning of the “cooks” note.  They’re kind of held stiffly there for that brief moment in between.  He’s orienting a couple different directions as he does this; he’s got his tail kind of stuck up into the air.

That flick of the wings at the beginning of the short song has the effect of flashing the white wing patches conspicuously, so that the audio and visual parts of the display are closely coordinated.  The BNA account suggests that both the long and the short songs may be used in courtship, but it gives few specifics.  I never heard the long song in conjunction with a visual courtship display.  All of this suggests that the short song might best be described as the “Display Coo” rather than the “second Advertising Coo” — though it is certainly given in many contexts other than the display, and far more frequently than the “Display Coos” of other dove species.  If the short song is equivalent to the “Display Coo” of other doves, then the rare two-note call could perhaps be the equivalent of the “Nest Coo.”

But another clue from Mexico might point in a slightly different direction.  As I was recording another courting male White-wing, I realized I was hearing two birds duetting from somewhere up in the tree, although only the wing-flashing male was visible.  One of the birds was doing the normal four-note short song, and the other was giving an abbreviated three-note version:

White-winged Dove three-note song, El Cajon, Sonora, Mexico, 6/30/2010.

This three-note song is clearly intermediate between the two-note Arizona recording and the typical short song.  The first note is almost identical to the Arizona bird’s: a breathy growl becoming a coo with an upward-and-downward  voice break.  The last note is slightly burry.  Take out that short middle note, and you’ve got a pretty close match to the mystery two-note song.

During this observation, I got the impression that the bird doing the wing-flashing was also the one producing the three-note song, but I couldn’t be entirely sure of that.  If I was mistaken, then it might have been the hidden bird, presumably a female, making the three-note song.  And that correlates with another clue hidden in the BNA account:

Female call is lower in volume, shorter, and slurred (Viers 1970).

No more details of female calls are mentioned, including whether they resemble the long song or the short song or both, or whether they may be given in response to the courtship displays of males.   We’re left with three possible explanations:

1. The two- and three-note songs may be given by males in courtship.  However, the four-note short song is also clearly given in this context, among others, which would mean the two- and three-note versions might be individual variants of or perhaps excited versions of the short song.
2. The two- and three-note songs may be the “Nest Coos” given by males.  However, both recordings I have of the shorter songs occur during duets, which is rather odd for a “Nest Coo.”
3. The two- and three-note songs may be the female version of the short song, given primarily during courtship duets.  This contradicts my impression that the wing-flashing male in Mexico was the one singing the modified song, but I may have been wrong about that.

The Big Reveal

I promised you a mystery, not a solution.  I don’t know which of the three interpretations is correct.  That will take more data, probably more observations and more recordings.  It’s another terrific example of how little we know about the sounds of some common birds, and how difficult it can be to try to match the descriptions of earlier naturalists with one’s own recordings and observations.

It’s also a terrific testimony for the importance of behavioral notes on audio recordings.  Most of the amateur sound recordists I know don’t spend much time talking into their microphones at the end of each cut, but they should.  Talk about what the bird was doing while you’re still in the field, when you’ve just watched it happen, before you head home and forget the details.  Specific behavioral information is more important than any other type of information you record.

Above all, this is a demonstration of the way in which I answer my own questions about bird sounds — by trying to cross-reference field observations, recordings, the scientific literature, and my own intuition.  It can be frustrating to spend so much time researching a vocalization without being able to come to one solid answer.  But it’s also thrilling to be this close to the forefront of knowledge, just because I was willing to spend time trying to answer a simple question about a common bird.

My recording of a Least Sandpiper also opened a BBC radio segment back in December, in an article on the crazy wave of vagrant birds that Britain had last year (including Least Sandpiper).  Unfortunately, you can’t listen to that show online — the BBC doesn’t roll that way — but you can read an online version of the article you’re interested in the boring old human-speech part of the broadcast.  (They didn’t bother transcribing what the Least Sandpiper had to say.)

For the record, I gave permission for the use of my sounds in these broadcasts at no cost, and without attribution.  I’m just happy to get bird sounds into radio listeners’ ears!

It was one of the last North American bird species to be described to science, in 1857.  Its nest was not found until 1901.  The first audio recording of its voice was not made until 1993.  And every summer, across most of its breeding range, it is the last species to arrive from the south, often not appearing until the end of June.

But most remarkably of all, it was the only North American migratory bird to enter the 21st century with the location of its wintering grounds still a complete mystery.

The migration routes and wintering grounds of Black Swifts have remained unknown to science until now. Photo composite by Bill Schmoker, Zapata Falls, Colorado, June 2008 (click for link).

By any measure, Black Swifts are bizarre.  They nest in the spray zone of waterfalls, sometimes behind the water, so that  juveniles may never have dry feathers between hatching and fledging.  They take to the air before dawn, spend the entire day foraging for flying insects at altitudes so high that they often cannot be seen with the naked eye, and frequently do not return to the nest until after dark.  Then they get up several times during the course of the night to regurgitate insects for their only child, who sat hungry and wet at home all day.

The high-flying habits of Black Swifts make them almost impossible to track during migration.  The parents stay at the nest until the chick is old enough to fly in August or September, and then they vanish, not to be seen again until the following May or June.  A few anecdotal observations and a couple of specimens have suggested that Black Swifts may migrate south along the California coast, and that at least some reach Costa Rica or Colombia in migration.  But no observations, specimens, or band recoveries have ever revealed where the bulk of the population spends the winter.  The species is not large enough to carry satellite radio trackers or transmitters, so the mystery has seemed destined to persist, barring a major advance in technology.

The spring migration routes of the three Black Swifts whose geolocators were recovered in 2010. Fig. 1 of Beason et al. (2012).

But in 2009, a group of researchers from Rocky Mountain Bird Observatory caught four Black Swifts in Colorado and fitted them with geolocators. Geolocators are not radio transmitters or satellite recievers, but rather primitive devices — just a light sensor, a digital clock, and a tiny memory chip. All they do is record the time of sunrise and sunset each day. But that’s all the information one needs to reveal where the bird has been. The time of local sunrise, measured against GMT, allows you to estimate your longitude — that is, what time zone you’re in. The length of the day, combined with the calendar date, tells you your latitude — that is, how far north or south of the equator you are.

There’s just one problem — since the geolocators can only record data, not transmit it, the only way to find out from the device where it’s been is to recapture the exact same bird a year after you saddle it with the tiny light-sensing backpack.

Knowing that Black Swifts have a very high fidelity to their nesting sites, the RMBO team hung mist nets at the two places where they had outfitted birds with geolocators the year before. It took three different trips over the course of the summer, but they managed to recover three out of the four geolocators — a remarkable 75% success rate. Today they announced the results: those three Black Swifts carried their little backpacks all the way to South America and back — specifically to the Amazon basin of western Brazil.

At right are the maps from the article published today in the Wilson Journal of Ornithology by Jason Beason, Carolyn Gunn, Kim Potter, Robert Sparks, and James Fox.  The white lines on the three maps are the northbound spring migration routes of the three swifts whose geolocators were recovered in 2010. Fall migration routes, unfortunately, could not be accurately mapped, because the period of fall migration too closely coincided with the autumnal equinox, when day length is equal at all latitudes, making it difficult to measure north-south  movement accurately.

The colored blotches in the western Amazon are the areas where the swifts likely spent most of the winter.  They’re blotchy because the geolocators aren’t terrifically accurate, and also because the swifts apparently  moved around a fair amount during the winter.  It’s possible that they roosted in caves or cliffs for the night and then roamed extensively during the day, but the researchers raise the tantalizing possibility that wintering Black Swifts may actually stay aloft 24 hours a day, based on the behavior of the related Common Swift of Eurasia, which may be on the wing for up to 9 months of the year — or even several consecutive years, in the case of non-breeding individuals!

The authors stress, however, that no conclusions about roosting behavior can be drawn from the current study.  If the wintering birds do roost in dark crevices like they do in summer, they could skew the geolocator data, which is based on light levels.  Extensive cloud cover could also be an issue.  There’s evidence of at least some errors in the migration tracks at right: the researchers stress that bird 554 did not, in fact, probably take a quick jaunt to the Pacific Ocean off of Baja California after arriving in Colorado — that data point is likely due to some type of irregular shading event that messed up the geolocator data.  Nevertheless, the generally strong agreement between the tracks of the three birds provide a reasonable level of confidence about the quality of the data.

The Black Swifts were estimated to cover between 210 and 240 miles per day, on average, during their southbound and northbound migrations.  More study needs to be done to determine whether their migration routes and wintering areas are typical of Black Swifts, or whether they are specific to the Colorado population.

For more information on the remarkable Black Swift, check out the book The Coolest Bird by late, great Colorado swift researcher Rich Levad, published online by the American Birding Association.

Literature Cited

Beason, J.P., C. Gunn, K.M. Potter, R.A. Sparks, and J.W. Fox. 2012. The Northern Black Swift: Migration Path and Wintering Area Revealed. Wilson Journal of Ornithology 124:1-8.

Black-capped Gnatcatcher, California Gulch, AZ, 5/16/2009. Photo courtesy of John Schwarz, Birdspix.com (click for link). This photo was taken only three days after my recordings from the same location, so it may be of the same individual.

Just 30 years ago, the dapper Black-capped Gnatcatcher was ultra-rare north of the Mexican border.  Today it can be found with some regularity in decent numbers in several different locations in Arizona and New Mexico.  But separating it from the more numerous Blue-gray Gnatcatchers can be a real challenge, especially in winter, when the males don’t sport their namesake caps.

Voice is a key field mark, but good descriptions and recordings of Black-capped Gnatcatcher vocalizations have until recently been in short supply, and confusion about the vocal differences between eastern and western Blue-gray Gnatcatchers has compounded the issue.  Add Black-tailed Gnatcatcher to the mix, plus a dash of the genus-wide tendency to say unpredictable things, and you’ve got a recipe for confusion.

We’ll try to alleviate some of that confusion today.

Black-capped Gnatcatcher whines

The single best way to identify a Black-capped Gnatcatcher is by listening for one of its most common calls, a distinctive polyphonic overslurred whine that reminds some people of a kitten’s meow:

Male Black-capped Gnatcatcher, California Gulch, AZ, 5/13/2009.

This typical version of the call is strikingly similar to the distinctive mew of the California Gnatcatcher, but California is not found in the same regions as Black-capped.  Of course, Black-capped calls are also variable.  Here’s a rather odd version:

Black-capped Gnatcatcher call (variant with upslurred ending), Alamos, Sonora, Mexico, 7/3/2010.

And here’s a downslurred variant:

Black-capped Gnatcatcher call (downslurred variant), Alamos, Sonora, Mexico, 6/26/2010.

(Here’s another downslurred example for good measure.)

Beware the Blue-grays!

Not only is Blue-gray the gnatcatcher that looks most like Black-capped, it’s also the one that can sound most similar — especially the western population.  As we saw in the last post, the simple song of western Blue-grays is composed of overslurred whiny notes.  Usually the overslurred whines of Blue-grays are organized into short series during bouts of the “simple song,” while the similar notes of Black-capped are often (but not always) given singly.

When Black-cappeds give downslurred whines, they may be especially difficult to distinguish from the standard calls of western Blue-grays:

Western Blue-gray Gnatcatcher calls, Fremont County, CO, 5/15/2008.

 Black-capped Gnatcatcher rough calls

In addition to its trademark whines, Black-capped Gnatcatcher also gives some rough notes, possibly in alarm or as part of the simple song.   These rough calls could be mistaken for the sounds of a Black-tailed Gnatcatcher.

Male Black-capped Gnatcatcher calling in response to my whistled pygmy-owl imitation, California Gulch, AZ, 5/13/2009.

Male Black-capped Gnatcatcher, California Gulch, AZ, 5/13/2009.

Beware the Black-taileds!

Among the western gnatcatchers, the Black-taileds are usually considered the ones with the most distinctive voices — rough, harsh, noisy, hoarse, unmusical, and rather unlike the higher-pitched, polyphonic, whiny voices of their congeners.  But the rough calls of the Black-cappeds above encroach on traditional Black-tailed territory.  The last call above, in fact, is virtually identical to some calls of Black-taileds, like this example:

Ultimately, we still know very little about the voice of Black-capped Gnatcatchers.  They certainly sing a complex song like that of Blue-grays.  They probably sing something like the simple song of that species as well, but what comprises that simple song isn’t clear — this recording may be an example of it.  Rough notes appear to indicate agitation in at least some cases, but perhaps not always.

By far the best indicator of a Black-capped Gnatcatcher is the classic overslurred whine.  My experience indicates that this call can be heard from about 80% of Black-capped Gnatcatchers within five minutes of observation.  However, the species often gives variant calls for several minutes in a row, including downslurred or noisy versions that resemble those of the other two gnatcatcher species.

The take-home message?  Though their “classic” call is distinctive, Black-capped Gnatcatchers are more vocally variable than many people have given them credit for.  Identifying one in the field may require careful listening and a good deal of patience.

Eastern Blue-gray Gnatcatcher, Liberty, Missouri, 4/16/2011. Photo by Big Dipper 2 (CC 2.0)

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”.

Simple song

Here’s the simple song of western populations, which Root called the “advertising song”:

Western Blue-gray Gnatcatcher song, Fremont County, CO, 5/15/2008.

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:

Eastern Blue-gray Gnatchatcher simple song, Bandera County, TX, 3/26/2008.

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.

Complex song

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.

Eastern Blue-gray Gnatcatcher complex song, Bandera County, TX, 3/26/2008.

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.

Calls

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:

Western Blue-gray Gnatcatcher call, Fremont County, CO, 5/15/2008.

Eastern Blue-gray Gnatcatcher calls, Scott County, MN, 6/13/2010.

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!

Chestnut-backed Chickadee, Vancouver, BC, 11/20/2010. Photo by Sean McCann (Creative Commons 2.0).

What do chickadees sound like?  Why, everybody knows they say “chick-a-dee-dee-dee,” of course.

These “chick-a-dee-dee-dees” are what many people (and many books) describe as the “calls” — not to be confused with the “songs,” which are usually understood to be the high clear whistled tunes sung by males in a territorial mood:

All chickadee species give “chick-a-dee” calls, but only three of them — Black-capped, Carolina, and Mountain  — have whistled songs.  Since these three species are the most widespread and familiar North American chickadees, many people tend to judge other chickadees by their standard.  “Lacks whistled song,” many field guides say of Mexican, Chestnut-backed, Boreal, and Gray-headed Chickadees.  “No song,” say others, or simply “song unknown.”

But the many researchers who have studied chickadee vocalizations for decades might disagree.  As far back as 1981, Millicent Ficken pointed out that an often-overlooked chickadee vocalization called the gargle may actually fulfill more of the traditional “song” functions than the whistled songs.

Unlike whistled songs, gargles can be heard from all North American chickadee species.  Like traditional songs, gargles are learned; Ficken notes that captive Black-capped Chickadee hatchlings do not develop proper gargles in the absence of an adult tutor.   Individual birds typically produce several different types of gargles, forming a repertoire.  In most or all species, the gargles are given primarily by males and  associated with dominance establishment and territorial defense.  They are extremely complex, being made up of many different note types, often with trills and repeated motifs.

For all these reasons, in the species that don’t also whistle, the gargles can be considered “the song”:

Although some field guides may frame them as the outliers, the chickadee species above are not the unusual ones when it comes to the traditional song/call distinction.  It’s the whistling chickadees that are unusual, because they have two different kinds of songs — not only whistles, but gargles as well:

The whistling chickadees are a perfect example of how the original “song/call” distinction fails to hold up in many species.  Not only can the whistle and the gargle both be called “songs,” but even the “chick-a-dee” calls could be considered songs by some criteria.  We should always be suspicious of the many generalizations about birds that we draw from the most common, widespread, and familiar species — remember, they may be the unusual ones.

Larkwire is a web-based tool that requires no downloading and can run on several kinds of smartphones as well as standard web browsers.  All the sounds are streaming.  You can play the demo version with just seven songs for free, but to get access to most of the sounds, you have to purchase a “songpack.”  The beginner songpack, with the 25 most common birds for whatever region of the country you’re in, costs $6.95.  They’ve formulated 15 different beginner songpacks for different regions of the country, which is a great idea, but it’s been implemented with a pretty serious eastern bias.  Boston, Philadelphia, and Baltimore are in three different regions (with 90% overlap in their most common birds) while Denver and Phoenix, despite their very different birds, have to share a region.

To get more songs, you pay more: the 100-species packs (eastern and western) cost $16.95.  To get the “Master Birder” set of 344 species, you’ll have to fork over a whopping $49.95.  On the bright side, 10% of every purchase goes toward conservation.

Once you’re loaded up with sounds, you can set Larkwire in motion in a couple different modes, all of which share the same basic idea: to introduce you to small sets of similar songs, and then quiz you repeatedly on those songs.  Even if you catch on quickly and open up a new group of songs, Larkwire keeps tossing in old familiar birds along with the new ones so that your memory stays fresh.  It also lets you customize the groups of songs you’ll be quizzed on in just about any way.

Larkwire draws immediate comparisons to the Peterson Birding By Ear series, which for the past 30 years has been the best song-learning tool on the market.  Both Larkwire and Birding By Ear take a similar initial approach, grouping soundalikes together for direct cross-comparison.  Sometimes Larkwire does this well, sometimes not-so-well.  For example, the full “Master Birder” songpack has one group called “Musical & Buzzy,” another one called “Delicate, Musical & Buzzy,” and a third called “Elaborate, Musical & Buzzy.”  The names and contents of all three seem rather odd:

When it comes to the quality of the written notes that direct the user’s attention to the differences between songs in a group, Larkwire falls consistently short of the standard set by the Birding By Ear series.  But it far surpasses Birding By Ear in its utility for easy cross-referencing, self-testing, and the matching of sounds with photos — and it also covers more species, with many more examples of each sound from across the continent.  Even so, most of the Arizona, south Texas, and Florida specialties are omitted, and so are ALL waterbirds, even Mallard and Killdeer.

The bottom line is that if you’re interested in spending the time it takes to memorize hundreds of bird sounds, Larkwire is clearly one of the best tools out there to help you do so.

Note: I have no commercial interest in Larkwire.

“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:

"Slate-colored" Fox Sparrow calls, Lake County, CO, 6/14/2011

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 [1] and the Macaulay Library [1 2].

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:

Agitated "tsip" calls from a Slate-colored Fox Sparrow, Lake County, CO, 6/14/2011

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.