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Splitting Mountain Chickadee

Splitting Mountain Chickadee

The AOU’s North American Checklist Committee has posted a set of proposals currently under consideration.  The biggest surprise is a proposed split of Mountain Chickadee into two new species:

  1. Gambel’s Chickadee (Poecile gambeli) in the Rocky Mountains and the Great Basin, including populations in eastern Washington and Oregon;
  2. Bailey’s Chickadee (Poecile baileyae) in the Sierra Nevada, the Cascades, and the California coastal mountains.

Until the AOU proposal appeared, a potential split of Mountain Chickadee was not even on my radar screen.  However, two different molecular studies have found evidence that the two groups of chickadees are genetically quite distinct, and they apparently differ slightly in appearance, with “Gambel’s” Chickadees having a slightly longer tail, slightly more white above the eyes, and a faint buffy tinge to the underparts and back.

"Gambel's" Mountain Chickadee, Sandia Crest, NM, 3/26/2008. Note the buffy underparts and broad eyestripe. Photo by J.N. Stuart (Creative Commons 2.0)."Bailey's" Mountain Chickadee, Yosemite National Park, CA, 11/24/2007. Note the gray underparts and narrow eyestripe. Photo by Yathin (Creative Commons 2.0).

In addition, the proposal mentions song differences.  Sadly, it provides scant evidence for this claim.  Here’s the entire discussion of vocalizations:

Miller (1934:163) reported on song differences that he detected between Mountain Chickadees from southern Utah (wasatchensis) and from California (abbreviatus or baileyae): “I note repeatedly that the songs of this chickadee [wasatchensis] consists of two groups of notes separated by three or more half tones of pitch. In contrast to this type of song are those of the races P. g. baileyae and abbreviatus in which the greatest interval of pitch with rare exceptions is no larger than one whole tone.”

This is flimsy evidence indeed.  The difference in pitch interval that Miller noted could potentially be significant, but it’s only one metric by which to measure the complex matrix of geographic variation in Mountain Chickadee vocalizations.  Mountain Chickadee’s vast geographic range comprises a balkanized patchwork of dozens of different dialect regions, as one would expect in a bird that learns its song.  Miller was a single naturalist noting a single difference between just two or three of these dialects, in an era before sound recording and spectrographic analysis.

Furthermore, the evidence I’ve found so far doesn’t even corroborate his original observation.  Here’s the most common dialect variant of “Bailey’s” Chickadee, the version of Mountain Chickadee song most likely to be heard all throughout the Sierra Nevada:

"Bailey's" Mountain Chickadee song, Lava Beds National Monument, California, 5/29/2002. Recording by Geoff Keller (LNS 120257).

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

Many observers in the region transliterate this (and similar songs) as “cheese-burger,” although there’s actually a short extra note in front of the “cheese” in most parts of the Sierra.  The “cheese” and “burger” parts of the song are separated by about a full step on average, with slight variations from place to place [1 2 3 4 5].  So far, so good — these recordings are mostly in line with Miller’s observations.

But the wide pitch intervals that Miller reported from southern Utah are certainly not representative of most “Gambel’s” Chickadees.  In this Borror Lab recording from northern Utah, the notes are quite close to one another in pitch, each about a half step lower than the last.  And most Mountain Chickadees in Colorado sing nearly monotone songs, like in this typical example:

Mountain Chickadee song, Larimer County, CO, 5/28/2008.

Here’s an example of a “Gambel’s” Chickadee from British Columbia that sings a songtype not unlike the Sierra Nevada “Bailey’s” song:

Meanwhile, here’s a “Bailey’s” from the heart of the Sierra Nevada that barely changes pitch at all, and here’s a “Gambel’s” from Wyoming that apparently sings two songtypes, one with a large pitch change and another that’s nearly monotone.

Perhaps the genetic data is clear enough to warrant a split of Mountain Chickadee, and perhaps vocalizations do differ systematically — they may even act as an isolating mechanism between the two groups.  But a far more in-depth study would be needed to demonstrate this.  On the basis of the evidence presented in the AOU proposal, I can see no reason at this time to add “vocalizations” to the list of reasons for the split.

Curve-billed Thrasher Identification

Curve-billed Thrasher Identification

The AOU checklist committee recently rejected a proposal to split the Curve-billed Thrasher into two species: the “Palmer’s” Thrasher (palmeri group) in Arizona and West Mexico, and the nominate or “Eastern” Curve-billed Thrasher (curvirostre group) in the rest of the bird’s range.

"Palmer's" (Western) Curve-billed Thrasher, Desert Botanical Garden, Scottsdale, AZ. Photo by Patrick Coin (Creative Commons 2.0).Nominate (Eastern) Curve-billed Thrasher, Colorado, by Fort Photo (Creative Commons 2.0).

Although very similar, the two groups can usually be distinguished by sight. In the photos above, note that the eastern bird (right) has a much whiter background color to the breast, resulting in stronger contrast with the breast spots; it also shows sharper and bolder white highlights in the wings and tail.  The stronger throat pattern, with a more distinct dark line bordering the white throat, may also be significant.  However, the much colder, grayer tone to the plumage overall is likely an artifact of photo lighting.

Interestingly, one of the committee members who voted “yes” on the split did so in large part because of differences in the call notes between the two forms, which I hadn’t seen discussed anywhere before:

YES. I now favor splitting palmeri – the clincher for me is that palmeri has distinct call note differences, a clear upslurred whit-wheet, as opposed to a two note whit-whit in which both notes are the same.

I have investigated this difference, and it seems to hold up across (at least) most of the species’ US range.  The vast majority of the call recordings I could find from well inside the range of “Palmer’s” Thrasher showed the same typical pattern: two upslurred whistles that started at the same pitch, with the second one ending much higher:

"Palmer's" Curve-billed Thrasher call, Catalina State Park, Pima County, AZ, 2/23/2008.

Whereas the call of eastern curvirostre-group Curve-billed Thrashers consist of nearly identical notes, both upslurred across a wide frequency range like the second note of the “Palmer’s” call:

Nominate eastern Curve-billed Thrasher call, Carlsbad Caverns National Park, Eddy County, NM, 3/30/2008.

Both groups of Curve-billed Thrashers give versions of this call with 3 or more notes, particularly when they are excited.  When the eastern curvirostre group does so, as you can see in the spectrogram above, all the notes tend to be similar.  When western palmeri birds extend their calls, the first note is usually of the stunted variety.  The third note (and any subsequent notes) tend to be like the second, but a little softer, so that the second note ends up getting the emphasis: “wit-WEET-weet”:

"Palmer's" Curve-billed Thrasher calls (3-noted version), Alamos, Sonora, 7/3/2010.

Some Curve-billed Thrashers in southeast Arizona give multi-note calls that are difficult to classify.  Here’s a bird from a few miles south of Eloy in Pinal County, where I believe the palmeri subspecies would be expected:

Atypical Curve-billed Thrasher calls recorded south of Eloy, Pinal County, AZ, 2/22/2008. Recording by Andrew Spencer.

Here’s some more from the same individual bird:

The two-note versions of this individual’s call tend to seem like the reverse of the typical palmeri pattern, with the second note quieter and less extensively upslurred than the others.  One might suppose this could be an intermediate bird, since the palmeri and curvirostre groups apparently overlap in southeast Arizona, but most educated guesses that I’ve seen have placed the overlap zone farther east, between Tucson and the New Mexico border.  I don’t believe this bird was identified visually to subspecies, so it remains a question mark for now.

Just to whet the appetite of the curious, here’s a Curve-billed Thrasher call from the Oaxaca valley in southern Mexico, which preliminary DNA studies showed as being distinct from either the palmeri or the curvirostre group (though apparently more closely allied with the latter).  Note again the “WEET-wit” pattern, which is the reverse of palmeri’s:

Obviously, more sampling is needed to fill in the many gaps in our knowledge of the Curve-billed Thrasher and its vocal variation.  Amateur recordists of the southwestern US and Mexico, this is your cue.

Band-winged Nightjar Feature

Band-winged Nightjar Feature

Band-winged Nightjar (subspecies decussatus), Rafan, Lambayeque, Peru. January 2010, copyright Christian Nunes

I’ll admit I was crushed when Nathan wrote a feature for xeno-canto before I did.  I have no one to blame but myself; it was pure laziness on my part that kept me from doing one.  After I got over the bruised ego from him being first I got my act in gear and wrote one of my own.  So if you want to read about the vocal variation in Band-winged Nightjars, check out my first xeno-canto feature.

Like Flycatchers and other suboscine passerines, Nightjars don’t learn their voices.  So distinct vocal variations may well have taxonomic implications.  In Band-winged Nightjar in particular there seems to be a good case for further study,  and potentially splitting the species.   For example, note how the differences in Whip-poor-will vocalizations recently played a role in the split of that species.

Finally, if any of you have recordings of Band-winged Nightjars you could upload to XC, especially of the decussatus, roraimae, or patagonicus subspecies that would be of great help!

The Genus Formerly Known as Aimophila

The Genus Formerly Known as Aimophila

Recently I explored some of the recent AOU species splits by comparing birdsongs.  Today I want to look at a genus that the AOU dramatically chopped and reshuffled: the sparrow genus Aimophila.

Aimophila has long troubled taxonomists.  On the one hand, it has traditionally included certain pairs of species — for example, Cassin’s and Botteri’s Sparrows, or Rufous-crowned and Rusty Sparrows — that look nearly identical.  On the other hand, it has also included birds that look radically different from one another.  In fact, taxonomists have never been able to establish a definitive set of features that distinguishes Aimophila from other sparrows.  Unsurprisingly, it turns out that not all the species in the genus share a common ancestry.

Still in Aimophila: Rufous-crowned Sparrow. Photo by Jerry Oldenettel (Creative Commons 2.0).Moved to Peucaea: Sumichrast's (Cinnamon-tailed) Sparrow. Photo by Jorge Montero (Creative Commons 2.0).Moved to Peucaea: Stripe-headed Sparrow. Photo by Len Blumin (Creative Commons 2.0).

A DNA study by DaCosta et al. (2009) recently showed that the members of Aimophila were not all each other’s closest relatives — a finding that typically portends a taxonomic rearrangement.  Largely on the basis of that study, the AOU recently split Aimophila three ways:

Remain in Aimophila

  1. Rufous-crowned Sparrow (Aimophila ruficeps)
  2. Rusty Sparrow (Aimophila rufescens)
  3. Oaxaca Sparrow (Aimophila notosticta)

Move to Peucaea (a resurrected genus)

  1. Cinnamon-tailed Sparrow (Peucaea sumichrasti)
  2. Rufous-winged Sparrow (Peucaea carpalis)
  3. Stripe-headed Sparrow (Peucaea ruficauda)
  4. Black-chested Sparrow (Peucaea humeralis)
  5. Bridled Sparrow (Peucaea mystacalis)
  6. Botteri’s Sparrow (Peucaea botterii)
  7. Cassin’s Sparrow (Peucaea cassinii)
  8. Bachman’s Sparrow (Peucaea aestivalis)

Join Sage and Black-throated Sparrows in Amphispiza

  1. Five-striped Sparrow (Amphispiza quinquestriata)

I’m going to save Five-striped Sparrow for another day, since it’s a complex topic — but let’s take a look at how the vocalizations of the other two groups give a clue to their taxonomic relationships.

Aimophila nasal chatters

A hallmark of the three species remaining in Aimophila is a short nasal call that often runs into a long fast chatter.  Here are examples from two of the three (the Rufous-crowned Sparrow chatter is at the end of the recording):

I couldn’t find online examples of the Oaxaca Sparrow chatter, but Howell and Webb say that it has one:

A slightly nasal, dry, scolding chatter shasha… or chehcheh… suggesting a wren; also a harsh, more excited, often prolonged chattering chii-i-i-i-i-i-ir, accelerating and slowing.

Peucaea rhythmic twitters

The species now in Peucaea don’t appear to give nasal chatters like those above, but many of them do give a unique “rhythmic twitter” — a rapid series of chip notes in which every fourth note or so is audibly different than the majority, giving the whole thing a unique rollicking rhythm.  The Black-chested Sparrow of Mexico provides perhaps the best example:

In its complexity, this call sounds much like a song, but the actual song of Black-chested Sparrow is described in Howell & Webb as a separate vocalization:

Song typically a single note followed by a rapid, liquid series of 8-16 notes sometimes accelerating into a trill: swiet, swieswieswieswie… or psu, susususu…, etc.

You can hear one strophe of Black-chested Sparrow song here (the very first vocalization on the cut; the rest is the rhythmic twitter).  Howell surmises that the rhythmic twitter may actually be a duet between two birds, and spectrographic analysis seems to support this view: in several examples on the Macaulay Library cut linked above, it seems that one bird often starts or finishes before the other.

Several other species of Peucaea apparently have rhythmic twitters (apparently often or usually duets) in addition to musical songs:

Cinnamon-tailed Sparrow

Rhythmic twitter:

Song:

Rufous-winged Sparrow

Rhythmic twitter:

Song:

Stripe-headed Sparrow

Rhythmic twitter:

Song:

Bridled Sparrow

Rhythmic twitter:

The song can be heard here.

The remaining species in Peucaea are more familiar to American birders: Bachman’s, Botteri’s and Cassin’s Sparrows.  They apparently don’t give rhythmic chatters quite the way their Mexican congeners do — or at least not as often — but the literature on all three species describes “excited songs” and/or “pair reunion chatters” that may well correspond to the “rhythmic twitters” above.  (There well may be a difference between “excited songs” and “twitter duets” in some of the above species, although I didn’t really draw the distinction this time around.  In particular, I know for a fact that only one Cinnamon-tailed Sparrow individual was involved in the production of the “rhythmic twitter” example above, and it was responding aggressively to my playback of the same vocalization — which sounds more like an “excited song” type of behavior than a “twitter duet.”  You know what that means — more study needed!)

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The Changes Are In

The Changes Are In

It’s July, and that means it’s time for the annual update to the American Ornithologists’ Union Checklist.  That means the splits I blogged about recently are now official.

Besides the high-profile splits of Winter Wren, Whip-poor-will, and Black Scoter, the checklist committee also did some major rearranging of scientific names, splitting a number of genera and reassigning several species to a new genus.  They do this whenever scientific studies (usually DNA studies these days) make it clear that birds currently classified in the same genus are not, in fact, each other’s closest relatives.  Although most such splits this time around were based on DNA evidence, vocalizations also support most splits.  Below we’ll take a quick survey of what’s changed and how audio was involved.

Species split

  1. Winter Wren is split into three species: Pacific Wren (Troglodytes pacificus) in northwestern North America; Winter Wren (Troglodytes hiemalis) in eastern North America; and Eurasian Wren (Troglodytes troglodytes) in the Old World.  Vocal differences were important in this split; see my older posts on how to separate Pacific from Winter Wrens by song and call.
  2. Whip-poor-will is split into Mexican Whip-poor-will (Caprimulgus arizonae) and Eastern Whip-poor-will (Caprimulgus vociferus). Vocal differences were important here as well; see my earlier post on this topic.
  3. Black Scoter is split into Black Scoter (Melanitta americana) in the New World and Common Scoter (Melanitta nigra) in the Old World.  Once again vocal differences were key, and once again you can hear them in an earlier post.

A couple of Latin American trogon species, the Greater Antillean Oriole, and the Elepaio of the Hawaiian islands were also split.

Changes in Genus

“Brown” Towhees Move to Melozone

Abert’s, Canyon, California, and White-throated Towhees will move from the genus Pipilo to Melozone, where they will join the Rusty-crowned, White-eared, and Prevost’s Ground-Sparrows. This genus split makes sense when you listen to the songs: the “brown” towhees sing with unmusical high-pitched trills and squeals that are very different from the rich, musical series of the “true” towhees.

“True” Towhees Remain in Pipilo

 

These species usually sing songs composed of 2-4 series of fairly musical notes — sometimes highly musical notes.  Some of them can be confused with each other, but rarely would they be confused with any of the “brown” towhee songs.

“Nashville” Warbler complex moves to Oreothlypis

Nashville, Virginia’s, Lucy’s, and Colima Warblers will move to the new genus Oreothlypis, along with the Orange-crowned and Tennessee Warblers.  This group is characterized by songs that are composed of 1-3 rapid (but not buzzy) trills.  The similarities are obvious on the spectrograms and to the ear:

Blue-winged and Golden-winged Warblers remain in Vermivora

These two species, plus their extinct relative the Bachman’s Warbler, remain in Vermivora.  All three are linked vocally by their very buzzy songs, quite similar to one another but quite different from those of the species leaving the genus.

Bachman’s Warbler songs can be heard at the Macaulay Library: [1 2]

Crescent-chested and Flame-throated Warblers move to Oreothlypis

This is one change that doesn’t seem to be supported by vocalizations.  These two Central American species were formerly in the genus Parula with (surprise) the parulas.  And their songs sound very like those species — high and buzzy — not at all like the songs of the other bird moved to Oreothlypis.

These embedded iframes are great, but they take up a lot of space, so we’ll continue on this theme tomorrow.

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Wings of Thunder

Wings of Thunder

Andrew’s recent post on Spruce Grouse sounds made this YouTube video into a particularly nice find.  Shot by birding guide Khanh Tran in Washington state, it documents the double wing-clap display of the “Franklin’s” subspecies of the Spruce Grouse, which is the form found in the Pacific Northwest, north to central British Columbia and Alberta.  The video will play in high resolution by default; I recommend clicking on the fullscreen icon.  At the end, the wing-clap portion of the video is replayed in slow motion, and appears to show that the bird makes the sound by clapping its wings together above its back as it descends:

These wing-claps, aptly compared to gunshots in the Sibley guide,  have never been documented in the widespread “Taiga” Spruce Grouse (subspecies canadensis).  Most female grouse are thought to be extremely picky about their mates’ displays; males that don’t exactly match their expectations may not get a second look.  Thus, display differences are thought to contribute to reproductive isolation of a couple of other closely related grouse species (Gunnison vs. Greater Sage-Grouse  and Dusky vs. Sooty Grouse).  The presence or absence of a couple of loud wing-claps seem like a reasonable mechanism for separating “Franklin’s” from “Taiga” Spruce Grouse.

Compare the above to this excellent (but lower-resolution) video from northern Minnesota that manages to capture, I think, all the displays of a nominate “Taiga” Spruce Grouse, including all the ones Andrew posted about.  Note the similarity of the display flight as the male comes down from his tree perch — he “stalls out” much like the Franklin’s does and changes wingbeat speed, but resists all temptation to wing-clap.  Instead he makes the much fainter “drumming” recorded by Andrew, which is essentially inaudible in this video.

If that video didn’t satisfy your thirst for watching “Taiga” Spruce Grouse, check out the sequels (1 2 3).

Very little information on the display of Franklin’s Grouse is easily available; Khanh Tran’s video appears to be the only one of its kind online.  The Macaulay Library has a fairly extensive collection of Spruce Grouse recordings (both audio and video), but they all apparently pertain to the Taiga form.  Although Franklin’s and “Taiga” Spruce Grouse were considered separate species at one point, they were lumped in the mid-20th century due to reports of hybridization and introgression in their contact zone in British Columbia and Alberta.  As far as I can tell, no new information on this contact zone has surfaced in the scientific literature for more than fifty years, so there’s not much I can say about it.  However, molecular phylogenies of the grouse by Gutierrez et al. (2000) and Drovetski (2002) both provided genetic evidence for a split of Spruce Grouse, and David Sibley recently listed it as one of the 10 most likely upcoming splits.  But the group hasn’t been as well-studied as the Blue Grouse complex (now split again into Dusky and Sooty Grouse), so the checklist committee may want to reserve judgment for now.

Meanwhile, recordists wanting to make a difference in taxonomic research might schedule a trip to that legendary contact zone in Alberta and northern BC!

lWeoWtEacBE
Boat-billed Flycatcher Feature

Boat-billed Flycatcher Feature

Boat-billed Flycatcher, Horto Florestal de São Paulo, Brazil. Photo by Dario Sanches (Creative Commons 2.0). Click for link.

I just published my first feature article for Xeno-Canto.  I figured I should give their blogging functionality a try, and I’m happy with the result.  My subject is geographic differences in the vocalizations of the Boat-billed Flycatcher (Megarynchus pitangua), a Central and South American species that looks much like the Great Kiskadee of south Texas.

For reasons I explained in my recent post on hybrid flycatchers, vocal differences in flycatchers are likely to represent strong genetic differences.  I noticed some time ago that Boat-billed Flycatchers in Central America make some distinctive sounds that Boat-billed Flycatchers in South America don’t make, and vice versa.  I thought I would be able to write a quick feature recommending a split — a la my Gray Hawk posts [1 2] — but as I started writing, I realized that Boat-billed Flycatchers make a number of different sounds, some of them geographically variable, others apparently not.  It took me far longer to complete my project than I anticipated, which is one of the reasons why you’ve seen Earbirding go so long without a new post!

So head on over to Xeno-Canto’s feature page to check out my work.  As always, I’d love to hear what you think!

Whip Split!

Whip Split!

"Eastern" Whip-poor-will. Painting by Louis Agassiz Fuertes, from The Birds of New York (1910). Public domain.

According to the grapevine, the AOU Checklist Committee has voted to split Whip-poor-will into two species. This split has been long anticipated, as the eastern and southwestern forms breed a thousand miles apart in different habitats, show slight average differences in size and plumage, and (most importantly for this blog) sing slightly different songs.

One of the primary lines of evidence cited in the split proposal was the recent publication of a molecular phylogeny of the nightjars by Han et al. (2010).  Among many other species, the study looked at the two populations of Whip-poor-will (the eastern vociferus group and the arizonae group of the Mexican highlands), along with their close relative the Dusky Nightjar of Costa Rica (Caprimulgus saturatus).  The study says that the three taxa “form a group… but their inter-relationships remain unresolved. This suggests that these three taxa should be given equivalent taxonomic status.”  In other words, they recommend either splitting the Whip-poor-will, or lumping it with Dusky Nightjar.

Evidently the committee preferred the former option.  No word yet on what they chose for names, so I’ll call them “Eastern” and “Mexican” for now.  Here is a sampling of the songs of both forms, plus the Dusky Nightjar for comparison:

"Eastern" Whip-poor-will, Madison County, AR, 4/26/2009. Recording by Andrew Spencer.
"Eastern" Whip-poor-will, Madison County, AR, 4/26/2009. Recording by Andrew Spencer.
"Mexican" Whip-poor-will, Cochise County, AZ, date.
"Mexican" Whip-poor-will, Cochise County, AZ, 5/11/2009.
Dusky Nightjar, San Jose province, Costa Rica, March 2010. Recording by Arch McCallum.

The three song samples above progress through the taxa from north to south.  Note how with each successive southward jump, the song elements become longer, more widely spaced (both within and between strophes), and burrier (more squiggly on the spectrogram).  It’s clear that these three taxa are closely related, but it’s also easy to tell them apart, even by ear, primarily by speed and level of burriness.  However, it seems to me that the Dusky Nightjar is more different from the two North American forms than they are from one another; in addition to being much slower, it is also significantly higher-pitched.

Note that if the AOU accepts the recommendations of Han et al. when it comes to splitting genera, then the whole Whip-poor-will group (along with Chuck-will’s-widow, Buff-collared Nightjar, and possibly Common Poorwill) will be moved from the genus Caprimulgus into Antrostomus — but no such proposal is currently before the committee as far as I know.

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Eastern & Western Marsh Wrens

Eastern & Western Marsh Wrens

Eastern & Western Marsh Wrens sing slightly different songs, and may well be two different cryptic species. Many birders are aware of this in the vague sense, but haven’t taken the time to figure out how to tell the two forms apart.

mawrwestmawreast
Western Marsh Wren, Marin County, CA, 4/18/2009. Photo by Len Blumin (Creative Commons 2.0).Eastern Marsh Wren, Rockingham County, NH, 5/2/2007. Photo by Scott A. Young (Creative Commons 2.0).

As the above photos show, identification by ear is going to be much easier than identification by eye  — although these photos do nicely illustrate the slight average differences in crown color (browner in the west, blacker in the east).

So far, no one has reported any differences in the calls that the two Marsh Wrens make outside the breeding season, so this post will focus on songs.  At first listen, the two forms can sound extremely similar.  They both sing with the same pattern (that is, a couple of introductory notes followed by an unmusical trill):

Western Marsh Wren

Eastern Marsh Wren

Introductory notes

The easiest and most reliable way to separate the two forms is to listen to the introductory notes.  The introductory notes of Western Marsh Wrens almost always consist of two quick, low, noisy “tuk” sounds. The second “tuk” usually runs right up against the start of the trill: “tuk tukRRRRRRRRRR.”  Eastern Marsh Wrens, by contrast, very often start with a single nasal and/or buzzy note, which might be transliterated as “beer” or “bzt.” Listen for the difference in the songs above.

Some Eastern birds sing more complex introductions, giving 2-4 different kinds of introductory notes before the trill. Some of them — particularly in the far eastern part of their range, and especially coastal birds — can include so many different kinds of introductory notes that the overall impression is of a half-second warble preceding the final trill.  They also frequently include some of these notes after the trill.  Here’s a great example from upstate New York.

In another example from Florida, the bird goes crazy with high-pitched frantic warbles both before and after the trill; they may sound like distant fighting Killdeers, but they’re all Marsh Wren notes.

Tone quality

The tone quality of trills provides another important distinction. Western birds sing mostly noisy, unmusical notes, almost all of which sound like they could have been made by a typewriter or a stock ticker. The trills of an Eastern bird, meanwhile, tend to be more musical, although it’s a stretch to apply the word “musical” even to an Eastern Marsh Wren, since, at their loveliest, their trills tend to sound like someone rapidly shaking a fistful of coins. Nevertheless, listen closely to an Eastern trill for semi-musical “clinking” sounds or “piping” notes mixed in with other kinds of sounds.

Repertoire size

Both Eastern and Western Marsh Wrens sing with a repertoire of multiple song types, and they almost never sing the same song type twice in a row, preferring instead to cycle through almost their entire repertoire before repeating. According to Kroodsma & Verner (1997), Western males sing far more song types (100-200) than do Eastern males (40-60), but don’t bother trying to count them; instead, listen to the quality and complexity of the introductory notes and the trill.

Those familiar with Sedge Wrens may notice that Western Marsh Wren songs can be quite similar to songs of Sedge Wren, while Eastern Marsh Wren songs are less similar. However, Sedge Wrens can often be distinguished by their tendency to repeat one song type over and over again before switching to another. Unlike Marsh Wrens, they only cycle through their repertoires when excited, “during the dawn hour or during intense countersinging” (BNA).  Here’s a Sedge Wren for comparison:

New Crossbill Compendium

New Crossbill Compendium

Red Crossbill, type unknown. Larimer County, CO. Photo by Andrew Spencer
Red Crossbill, type unknown. Larimer County, CO. Photo by Andrew Spencer

Ken Irwin is a household name — at least among the bedlamites who think untangling the mysteries of Red Crossbill call types is a fun and worthwhile activity.  Ken has haunted the seaside spruces of California’s Patricks Point State Park for years, tracking the Red Crossbills that wander in and out of the park, recording their vocalizations, capturing and measuring them, and following their nesting cycles.  According to a couple of people I talked to, he may know the individual birds by name, and rumor has it that he is close to being accepted among the crossbills as an adopted member of their tribe.

Ken is best known for discovering a new call type (Type 10), and his paper describing it is coming out in the next issue of Western Birds (which, incidentally, will also include an article on phoebe vocalizations by Arch McCallum and me — more on that later).  When I talked to Ken on the phone last year, he was also hard at work on a website that would include sound files of all the types, their excitement calls, their begging calls, their songs, etcetera.

Now that website is up, and everyone interested in crossbills should go see it.  It’s a work in progress — but even in its current form, at about 14,000 words, it’s more than a little overwhelming.  Nevertheless I recommend girding your loins and wading in.  Irwin’s site is the most important addition to the web-based crossbill literature in years.

The recordings are probably the most important contribution made by the site, and they are both good and bad.  Here’s the good news:

  • there are a lot of them;
  • they put Type 6 and Type 7 on the web for the first time (outside Jeff Groth’s original site from 1996, where all the recordings are so short and so heavily edited that they don’t really count in my opinion);
  • there are several nice head-to-head comparisons of different types;
  • most of them include lots of examples of individual birds, so that you can quickly get a strong sense of the limits of individual variation within the types;
  • they include many recordings of lesser-known vocalizations like excitement calls or “toops”, chitter calls, and songs.

Here are some things I liked less about the site:

  • The organization is confusing, and it got more so as the page went on.  The information on this one page should have been split onto several linked pages, and was apparently intended to be.  This may improve with future revisions.
  • Personally, I feel that Irwin’s word descriptions of the different calls are uneven in quality and ultimately unsuccessful, but then I have this reaction to most word descriptions of crossbill calls.
  • The recordings have been a little too heavily edited for my taste, so that the birds sound too mechanical, not quite like they would in the field.  Since Irwin typically includes 2-3 calls per individual bird, the overall effect is much better than that of Jeff Groth’s site, but if he had included longer cuts with less editing, I think his recordings could have been even more useful.
  • The spectrograms are full-contrast — bicolored black-and-white instead of grayscale — and therefore less informative than they should be.

When it comes to the science — the validity of Type 10 in general, Irwin’s boundaries for Type 10, and his conclusions regarding crossbill song — I’m going to have to postpone judgment for a while.  When I see his Western Birds paper, I’ll post again.  Until then, when you’ve got a little free time and extra brainpower, head over to his page and start the long process of digesting the enormous amount of information that he’s published — and thank him for it if you get the chance.