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Category: Identification

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.

King and Clapper Rails

King and Clapper Rails

King Rail, Pike County, Missouri. Photo by Jim Rathert, USFWS (public domain). Click to enlarge

The two largest rails in the United States are so similar in appearance and vocalizations that they have at times been considered a single species.  In general the King Rail is a more brightly-colored bird of freshwater marshes, while the Clapper is a duller bird of coastal salt marshes.

But even this statement requires a few caveats. For one thing, Gulf Coast Clappers are brighter than East Coast Clappers, and the disjunct populations of “Light-footed” and “Yuma” Clappers in California and Arizona are brighter still, bright enough to have been considered subspecies of King Rail by some authors. Furthermore, King and Clapper Rails have been known to hybridize in brackish marshes where their ranges meet, spawning the dreaded “Cling Rails” — birds presumably intermediate in all respects, and not safely identified in the field, even when you can see them — which is not very often, for these ghosts of the cattails.

Most of the time, the presence of one of these rails is announced solely by their loud, unmusical calls, leaving us to identify them solely by voice. It isn’t always possible, but today we’ll talk about when and how it can be done.

The “Kek” Series

For humans, this vocalization is about as exciting as listening to a six-year-old incessantly rap a stick against a wooden fence.  For female rails, it must be quite an aphrodisiac, because it’s the primary way that males attract mates in early spring.  It’s typically heard for a fairly brief period out of the year, and given only rarely after the singer is paired.

Male Kings and male Clappers “sing” with the same notes — the key to identifying them is to listen to the speed of their calls.  Here’s a useful snippet from the Sibley Guide to Birds:

a series of unmusical kek notes, slower at beginning and end; the tempo of the fastest portion is useful for species identification. […] Individuals may give faster or slower calls depending on mood, but such departures are usually brief.  Long, consistent bouts of typical calls can be reliably identified.

According to Sibley, eastern Clapper Rails “kek” at about 4-5 notes per second, while Kings are slower, usually 2 notes per second.  In a careful survey of all the rail recordings I could find online, I found the differences to be consistently smaller than this. I found some very excited Clappers reaching 5 notes per second, but an extended listen to most birds will find them averaging between 3 and 4 notes per second in the fastest parts of their series.

Kings, meanwhile, seem to average between 2 and 3 notes per second.

But even they can get up pretty far into Clapper speed if they feel particularly motivated.  I’m assuming this one is safely called a King, since it was recorded just outside Columbus, Ohio:

It’s clear that fast Kings overlap with slow Clappers (or is it that excited Kings overlap with bored Clappers?). However, I agree with Sibley’s basic point: an extended listen to a bird should provide, at least, a good strong clue to its identification.

Grunt Series

You are more likely to hear this vocalization than the “Kek” Series.  It’s given by both sexes almost year-round, as a pair contact call and as a way of mediating territorial disputes with other pairs. Any loud noise may set off a Grunt Series, and one grunting rail often sets off another. Mated pairs may perform extended, unsynchronized grunt duets, one starting slightly after the other, in one of nature’s least aesthetically pleasing romantic gestures. These duets tend to go on longer than solo versions, and are less likely to accelerate at the end.

The Grunt Series of the two species, like the “Kek” Series, are made of similar notes and are best distinguished by speed. Again the Clapper is the faster bird, and again I’ve found there to be more overlap between the species than reported in Sibley: Clappers appear to average 4-6 notes per second, while Kings clock in at 3-5 notes per second. This range of overlap is great enough to suggest that only the fastest of Clappers and the slowest of Kings are safely identifiable by this call.

 

“Kek-burrs”

In the 1980s, Richard Zembal and Barbara Massey were the first to discover the meaning of this sound.  They were observing two color-banded pairs of “Light-footed” Clapper Rails in California. One morning, one of the males was killed by a Red-tailed Hawk.  Two days later, his mate (#421) began giving the “Kek-burr” call. By that same evening, she had succeeded in stealing the sole remaining male (#443):

From 1723 to 1843 that first evening they clappered [grunted] in duet 12 times and were seen copulating twice. The newly abandoned female, #442, began to kek-burr on the following morning. During that day and the following one, #443 divided his time between the two females. Without the aid of a full-time mate, #421 abandoned her nest. Each of the females, once alone, eventually kek-burred when #443 was with the other one, and #443 responded every time by returning to the calling female, often quickly. We witnessed #443 respond to kek-burring 11 times in 36.1 h of observations over 4 days. During one exchange he traveled the 190 m to the calling female within 18 min of the onset of kek-burring. When another male appeared on the fourth day, #443 returned to #442, #421 settled in with the new arrival making use of the same nest), and kek-burring ceased.

Thus, Zembal and Massey concluded that the “Kek-burr” is the female’s equivalent of the “Kek” Series — her way of advertising a burning urge to mate.

Females of both species give nearly identical “Kek-burr” calls, and I do not know of any way to separate the species by this call. Excited birds may give many rapid “Keks” before the burr; in some situations, the burr is given separately.

Screech

This is the vocalization that Sibley refers to as “a raucous squawk like a startled chicken”.  It’s not quite clear what motivates this call, but in both species it varies from a grunt to a squeak, and there do not appear to be any significant differences between the two species’ versions.

 Hoot

This rarely-heard call is apparently given by alarmed rails near the nest.  There are very few recordings of this sound, but you can hear the hoot of a Clapper Rail here.  Meanwhile, this recording at the Macaulay Library may represent the hoot of King Rail, but the bird making the sound was not seen, so it’s not even certain that the sound was made by a rail.

If you can shed any light on the mysterious Macaulay recording from Florida, or on the hooting calls of rails in general, please let me know.  If you’ve got recordings, I’d love to hear them.

Update 8/21/12

I just learned about recent research into the King/Clapper Rail complex: a 2012 Ph.D. dissertation by James Maley that not only found a solid genetic distinction between King and Clapper Rails (further demonstrated by this recent paper), but also found that West Coast “Clapper Rails” are part of a distinct lineage that also includes the tenuirostris “King Rails” of central Mexico. All these are separate from the longirostris group in South America.  Caribbean birds cluster with North American Clapper Rails.

Thus, it seems there’s a good case not only for keeping King and Clapper Rail separate, but further splitting Clapper Rail into 3 or 4 species. In both proposals, we’d end up with 3 species of large rail in North America: King, “eastern” Clapper, and “western” Clapper.  See the recent discussion on BirdForum for a little more info.

How Fast Is That Vireo Singing?

How Fast Is That Vireo Singing?

Gray Vireo, Rabbit Valley, Mesa Co., Colorado, May 2012 (copyright Andrew Spencer)

I can still remember the first time I heard a vireo “complex song”.  It was after completing a transect for Rocky Mountain Bird Observatory  in San Miguel county, Colorado, as I was walking through some pinyon-juniper forest, looking for things to record.  I found a singing Plumbeous Vireo, and set up to record it singing.  No sooner I had turned on the recorder, though, when it started belting out this crazy run-on jumbled song!  I was taken completely by surprise, not even knowing Plumbeous Vireos had it in them to sing so awesomely.

Since that day I’ve heard complex song from many vireo species, but it’s still something I don’t hear very often, and a treat whenever I do.  This type of vireo song is mentioned fairly extensively in BNA, often under different names.  For Bell’s and Black-capped Vireo it’s called “courtship song”, and said to be given when the male is closely associated with the female bird.  For other species, such as Plumbeous Vireo, it’s called “complex song”, and said to be given in a variety of circumstances.  In my experience, though, it’s most often given by agitated birds, either after playback, or after an encounter with another member of their species.   Occasionally a song that is either complex song, or possibly subsong, is heard from birds during fall migration as well.

Most vireo complex songs tend to follow a pattern, with song-like phrases mixed with high, squeaky notes.  There appears to be some variability, with a higher agitation rate correlating to fewer song-like notes, more high-pitched notes, a faster pace, and sometimes a longer strophe length.  The Solitary Vireo complex, Gray, Warbling, and Yellow-throated Vireos all fall into this broad pattern.  Hutton’s Vireo also seems to belong in this group, though like its primary song, its complex song is also atypical.

Black-capped and Bell’s Vireos seem to give more discrete complex songs, called courtship song in BNA for both these species.  In both species the complex song is reminiscent of their primary song, but quieter, faster, and more jumbled sounding, but without the long, continuous run-on character of the above group and without the incorporated high-pitched squeaky notes.  White-eyed Vireo may also fall into this group, though it’s song seems to have more call-like elements and is more run-on.

A third group, made up on Red-eyed and Black-whiskered (and presumably Philadelphia) Vireos seems to rarely give a complex song at all.  Indeed, BNA doesn’t mention such a vocalization for Philadelphia or Red-eyed Vireo, and only briefly for Black-whiskered.  What I’ve heard from Red-eyed sounded more like the complex songs of the first group than the second, but in general seem less well differentiated from the primary song.

Below are examples of complex songs for every species for which I could find recordings.  Needless to say, if any of you reading this have recordings of species not represented here, or more examples of any of these species, please let me know!

Plumbeous Vireo

Probably because I consider it the “default” vireo complex song I’m going to cover this species first.  All of the vireos of the Solitary Vireo complex sing similar complex songs; typically these are fast, jumbled series of song-like notes, call-like notes, and high-pitched squeaky notes.
Blue-headed Vireo

The complex song of the eastern representative of the Solitary Vireo complex sounds similar to Plumbeous Vireo, and there are perhaps more recordings of complex song from this species than any other.  In addition to the examples from xeno-canto below, the Macaulay Library has three cuts: ML#84774, 84775, and 100870.
Cassin’s Vireo

The complex song of this species is like the above two in broad details.  The only recording I was able to find was one at the Macaulay Library: ML#105665
Yellow-throated Vireo

There is remarkably little information on the complex song of Yellow-throated Vireo. Macaulay has two cuts (ML#164094 and ML#73885) of sounds tending towards complex song, and it seems like it would fall into the same mold as the Solitary Vireo group.
Gray Vireo

From the limited sample size of the complex song of this local western species it seems that it sings this vocalization with more distinct song-like notes, mixed with high-pitched squeaky notes, but without the harsh call-like notes of the Solitary Vireo complex.  BNA says of this vocalization “most frequently heard on breeding grounds (central Arizona and w. Texas), but also heard on wintering grounds in Big Bend region, Texas (JCB) and Sonora, Mexico.”
White-eyed Vireo

Of all the vireo species, the complex song of White-eyed Vireo is perhaps the most striking.  It is a remarkable series of run-on calls, mixing song-like elements, call-like elements, and things in between.  BNA calls this vocalization “rambling song”, and says “Rambling Song is produced by adult males in a variety of contexts and frequently by immature birds.”
Warbling Vireo

As if the song of this bird wasn’t complex enough already! The few times I’ve heard Warbling Vireo complex song it fell into the general mold of this vocalization type: song-like notes mixed with higher pitched squeaky notes. The examples I’ve heard don’t seem to mix in any call-like notes. BNA doesn’t even mention this song type for this species, and given the number of Warbling Vireos I’ve seen and heard and how rarely I’ve heard complex song from them I suspect this is a relatively rarely given vocalization.
Hutton’s Vireo

A somewhat atypical species of Vireo by North American standards, the complex song of Hutton’s Vireo falls into the same category.  Like the others above, however, it contains song-like elements and high-pitched squeaky notes.  Overall, though, it is a slower song than the other vireo species, and differs less from the primary song in this regard.  BNA makes no mention of complex song for Hutton’s Vireo.
Bell’s Vireo

BNA calls the complex song of Bell’s Vireo “courtship song”, and says that it is given when the male is in close proximity to the female. That, coupled with the distinctive nature of this vocalization (it tends to come in more discrete phrases without either the high-pitched squeaky notes or call-like notes given in other vireo complex songs) suggests that it falls into another sub-group of vireo complex songs.
Black-capped Vireo

Black-capped Vireo complex song tends more towards that of Bell’s Vireo than that of other vireo species, but seems to contain more calls and fewer song-like elements. It almost sounds like a mix between Bell’s and White-eyed Vireo fast songs. Like in Bell’s Vireo, BNA calls this vocalization “courtship song” and says it is mostly given when the male is in close proximity to the female bird.
Red-eyed Vireo

The closest I can find to a recordings of the complex song for this species are linked below.  I’ve heard other instances of complex song by Red-eyed Vireo that tend a bit more towards the Solitary Vireo type, but in general it seems that this species has more song-like notes in its complex song, few if any call-like notes, and fewer of the high-pitched squeaky notes.  Given how common this bird is, and how many recordings of it are available, I believe that complex song is very rarely given by this species.

Philadelphia Vireo, Two Buttes Reservoir, Colorado (copyright Glenn Walbek)
Other species

Now we get to the fun part of the blog post – what do we still need?  I have been completely unable to find any recordings of the complex song of either Philadelphia Vireo (BNA describes a faster, more complex vocalization, but I am not convinced that this is actually complex song) or Black-whiskered Vireo (BNA describes a complex song, and I would bet money that it would sound like Red-eyed Vireo).  And even the other vireo species don’t have their complex songs very well documented.  How much more jumbled and call filled does the fast song of Red-eyed Vireo get?  How about Yellow-throated Vireo?  These kinds of questions will take someone being out in the field at the right time and the right place, and having a mic to ready to get it on tape!
Identifying Eastern and Western Warbling Vireos

Identifying Eastern and Western Warbling Vireos

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.

A Dove Detective Story

A Dove Detective Story

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.

Identifying Black-capped Gnatcatchers

Identifying Black-capped Gnatcatchers

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 and Western Blue-gray Gnatcatchers

Eastern and Western Blue-gray Gnatcatchers

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!

Fox Sparrow, Part 2: Alarm & Contact Calls

Fox Sparrow, Part 2: Alarm & Contact Calls

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:

"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.

Fox Sparrow, Part 1: Flight Calls

Fox Sparrow, Part 1: Flight Calls

"Red" Fox Sparrow, Kane County, IL, 10/17/2010. Photo by Ken Schneider (Creative Commons 2.0).

"Sooty" Fox Sparrow, British Colombia, 2/4/2008. Photo by Rick Leche (Creative Commons 2.0).

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.

Breeding ranges of the four Fox Sparrow groups. Map in the public domain per Wikipedia (click for link).

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.

Flight call

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:

Comparisons of flight calls of Fox Sparrow populations.

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 1: Sooty Fox Sparrow flight call, Coos County, OR, 3/26/1989. Macaulay Library #44860
  • Calls 2-5: Thick-billed Fox Sparrow flight calls, California, Macaulay Library #48832
  • 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 [1 2 3 4] 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:

  1. 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;
  2. Thick-billed/Slate-colored group (2-6): Lower-pitched, more shallowly underslurred, with a spectrogram like an open-mouthed smile;
  3. “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.