Female Blue-throated Hummingbirds may be easier to distinguish from Magnificent Hummingbirds by sound than by sight. Photo by Jerry Oldenettel (Creative Commons 2.0).
Last week I had the pleasure of attending the 2011 Western Field Ornithologists’ Conference in Sierra Vista, Arizona, where the highlight of my trip was the opportunity to view and record huge numbers of hummingbirds. At our first stop, Beatty’s Guest Ranch in Miller Canyon, the legendary row of 15+ feeders was a blur of wings, with at least three or four dozen hummingbirds in view at any given moment, and others whizzing in and out at all times. It took mere moments to rack up a species list that included Magnificent, Black-chinned, Anna’s, Rufous, and Broad-tailed, Violet-crowned, and Broad-billed Hummingbirds.
Shortly, however, it became clear that the huge numbers of hummingbirds were both a blessing and a curse. For one thing, it meant that the number of difficult-to-identify females and immatures was immense. For another thing, it turned rarity-spotting into a search for a hyperactive needle inside a speedy, swarming haystack.
A few minutes into our field trip, one of the leaders, the eminent Kimball Garrett, called out “Blue-throated Hummingbird!”
“Where?” I asked.
“Didn’t see it,” he replied. “Only heard it.”
And then I was able to hear it too: a high-pitched, clear, brief, piping whistle, totally different from the chips, chirps, sputters and buzzes coming from the rest of the hummingbird crowd:
Blue-throated Hummingbird calls, Cochise County, AZ, 8/19/2011.
With my ears more fully open, I began to listen to the other species, and I realized that their vocalizations were distinctive too. In fact, within minutes, I could identify each hummingbird to genus (and therefore usually to species as well) just by hearing it call. After I had mastered the Blue-throated’s unmistakeable “seek!”, the next sound I learned to pick out was the strong, sharp “chip” of the Magnificent, which sounded to me more like the “tewp” call of a Black or Eastern Phoebe than like a hummingbird:
Magnificent Hummingbird calls, Cochise County, AZ, 8/19/2011.
The calls of the Broad-billed Hummingbirds were also instantly recognizable: noisy “chit” and “chittit” notes, much like the calls of a Ruby-crowned Kinglet:
Broad-billed Hummingbird calls, Pima County, AZ, 5/13/2009.
The Black-chinneds took a little more practice to pick out, but their calls were distinctive too, a slightly more nasal version of the standard hummingbird “chip,” reminiscent of tennis shoes on a gym floor:
Black-chinned Hummingbird calls, Pima County, AZ, 5/13/2009.
The genus Selasphorus, meanwhile, which includes Rufous, Allen’s, and Broad-tailed Hummingbirds, tended to give itself away by mixing short electric buzzes with other sounds (a variety of chips and twitters, plus the musical trills of the males’ wings):
Broad-tailed Hummingbird chips, buzzes, and wing trill (in background at about 6 kHz). Larimer County, CO, 5/20/2008.Allen's Hummingbird buzzes and chips, Orange County, CA, 3/21/2009.
And the Violet-crowned Hummingbirds could be identified by their quiet, smacking “tik” notes, so brief that they barely show up on the spectrogram as hair-thin vertical lines:
Violet-crowned Hummingbird calls, Cochise County, AZ, 8/19/2011.
With all these species shooting by at once, it only took me a short time to learn which was which, and arm myself with an identification tool of enormous power. “Black-chinned,” I’d find myself saying, even before the drab female hummingbird came out from behind the bush, much less landed on the feeder for binocular views. Suddenly I was performing feats of identification that had seemed like magic when Kimball Garrett did them a few minutes previously. And all it took was a little ear training!
White-crowned Manakin, eastern Venezuela, copyright Nick Athanas (www.antpitta.com)
The neotropics are blessed with many families of birds that you can’t see in your neighborhood park up north. But perhaps none of these are more interesting, from an acoustical perspective, than manakins. They defy expectations when it comes to making sounds: some of them rub modified feathers together like a cricket, while others beat at the air, snap their wings against their body, or engage in elaborate, ritualized displays involving multiple birds making a smorgasbord of weird mechanical sounds. And some of them just sit there all day on one perch and say “nicky-the-greek” over and over and over again.
Being suboscines, manakins are thought to not learn their songs , instead having them hard-wired into their DNA. And as with other suboscines, this has important implications for their taxonomy when major differences between populations occur. In at least one manakin clade (White-ruffed and White-bibbed Manakins), differences in vocalizations and displays played a role in considering them separate species.
When it comes to sounds, the White-crowned Manakin (Pipra pipra) isn’t the most interesting of the family. Its displays are mundane compared to those of, say, Long-tailed Manakin. And the mechanical sounds it makes are limited and mostly simple. But it does appear to have a plethora of distinct vocal types that may well correspond to different species, despite the fact that they all look nearly or completely identical to each other in plumage.
A recent trip to the remote Cordillera del Condor in far southeastern Ecuador piqued my interest in this vocal variety when I heard a new vocal type, one I hadn’t even known existed until the day before. That brought the total vocal types that I knew of up to three, each replacing the other in very close proximity in a complex system of allopatry that is unlike any other species group in Ecuador. I was interested to see how many there really were if I listened to recordings from throughout their range. What I found shows that there are more to learn about manakins than just how they make their weird noises (which is what most recent manakin research has focused on)…complex taxonomical puzzles also remain to sweeten the pot. I’ve written a feature on xeno-canto detailing what I’ve found – take a look!
Guest post today by Walter Szeliga, who is starting to turn his audio recorder on some very interesting problems of identification and taxonomy.
Introduction
Sage Sparrow, 2 Feb 2010, location unknown. Streaking on the mantle suggests canescens or nevadensis. Photo by Dominic Sherony (Creative Commons 2.0).
The specific status of the Sage Sparrow in North America has been in question since the publication of Ridgway’s 1887 treatise A Manual of North American Birds. In that volume, he attaches a footnote to the entry for Amphispiza belli nevadensis (p. 427): “With scarcely any doubt a distinct species”. Further subspecific division of the Sage Sparrow occurred in 1905 with Grinnell’s publication of “The California Sage Sparrow,” in which he described a third subspecies, “Intermediate Bell Sparrow,” A. b. canescens (Latin for “turning gray”). In addition to these three subspecies, a fourth, A. b. clementeae (“San Clemente Sage Sparrow”) is endemic to San Clemente Island — which, as a live firing range for the Navy, is all but impossible for most people to visit.
Recently, modern techniques, such as genetic sequencing (Cicero and Johnson 2007), have suggested that Ridgway’s feeling may be correct. Furthermore, a recent article in Zootaxa (Klicka and Banks, 2011) essentially constitutes a formal proposal to elevate A. b. belli and A. b. nevadensis to species status, complete with a new generic name, Artemesiospiza.
However, whether A. b. canescens should be recognized as a species distinct from A. b. belli remains in question. For now, Klicka and Banks (2011) lump it in with A. b. belli. Were the Sage Sparrows to be split, more birders would surely wish to identify these different groups in the field.
But identifying these groups in the field is tricky. During the breeding season, there are only a few regions of the American West where Sage Sparrow subspecies come in contact — a small area near Bishop, California, where canescens meets nevadensis; and a thin strip of the eastern California Coast Range from near Parkfield southward to the Little San Bernardino Mountains, along which belli meets canescens. In this area belli and canescens prefer quite distinct habitats, canescens breeding in the saltbush (Atriplex sp.) found on the floor of the Mojave Desert and belli preferring mountain chaparral dominated by chamise (Adenostoma sp.).
Range of the three subspecies groups of Sage Sparrow. From Cicero (2010). Click to enlarge.
While Sage Sparrows on breeding territories can largely be identified to subspecies by range and habitat, the situation is quite different during migration and winter. The nominate A. b. belli, “Bell’s Sparrow,” is primarily restricted to the Coast Ranges of California and Baja California and is mostly sedentary, but its territory is invaded each winter by members of both canescens and nevadensis. In fact, these “winter” invasions begin very early for some canescens, which disperse after breeding to higher elevations in the range of belli as early as June (see Cicero 2010).
Thus, vocal and visual differences are frequently required to separate the three mainland Sage Sparrows to subspecies. Fortunately, there are some plumage differences that could prove useful in the field.
Plumage differences
A. b. belli lacks distinct streaking on the mantle, while A. b. nevadensis shows streaking on the mantle.
A. b. belli has a distinct black malar stripe, while A. b. nevadensis shows a less prominent pale gray malar stripe.
A. b. belli shows a greater contrast between the head and body, with a darker gray head contrasting with a brownish body, while nevadensis is paler overall, with less contrast.
In the hand, nevadensis is a distinctly larger and longer-winged bird than belli, features consistent with the greater migratory distance of nevadensis. Unfortunately, size differences are all but useless under field conditions.
Notice that all of the field marks mentioned so far involve separating A. b. belli from A. b. nevadensis. In nearly all of the categories mentioned above, A. b. canescens show features intermediate between belli and nevadensis; hence Grinnell’s suggested common name of “Intermediate Sage Sparrow”. For good comparative photos of all three subspecies, check out Robert Royce’s photo galleries of belli, canescens, and nevadensis.
That brings us to vocalizations.
“Bell’s” Sage Sparrow (Amphispiza belli belli)
First, let’s look at a song from A. b. belli. A cursory glance at the spectrogram reveals a complex jumble of upslurred and downslurred notes on different pitches, for the most part lacking trills or buzzes of any significant length. As in other Sage Sparrows, songs from individual birds tend to be highly stereotyped, with most birds singing only one songtype and rarely giving shorter incomplete versions of this songtype.
"Bell's" Sparrow song (Amphispiza belli belli), Castaic, California, 4/15/2011. Recording by Walter Szeliga"Bell's" Sage Sparrow, Mendocino County, CA, 5/22/2001. Recording by Geoff Keller (LNS 118847). Click to listen.
Moving on to A. b. nevadensis, we immediately notice a difference. The spectrograms show prominent trills or buzzy notes, most of which cover a fairly broad frequency range. The cadence of the song is different, the mix of quick short notes and longer buzzes giving it a stop-and-go, herky-jerky rhythm. Note the tendency for the ending to recapitulate the first part of the song, a tendency shared by many males in every subspecies group.
Song of "Interior" Sage Sparrow, Amphispiza belli nevadensis. Montrose County, Colorado, 4/12/2008. Recording by Nathan Pieplow
Here’s another nevadensis Sage Sparrow from Dolores County, Colorado:
Song of "Interior" Sage Sparrow, Dolores County, CO, 5/12/2008. Recording by Nathan Pieplow
And here’s a gallery of Xeno-Canto uploads of this subspecies:
A typical nevadensis song is fairly easily distinguished fromclassic examples of belli by its lower pitch, richer burry texture thanks to the trilled notes, and more syncopated rhythm. However, note that a few nevadensis songs, like Tayler Brooks’ recording at lower left, seem approach those of belli in these characteristics and might be difficult to identify in the field in the absence of other clues.
Interestingly, analysis of song length, and number of notes per song suggest that A. b. nevadensis has the longest song (~2.1 seconds, 8 notes per second), contrary to the suggestion in the Sibley Guide. In fairness though, individuals from A. b. belli do sing more notes per second (12 notes per second, ~1.4 seconds per song) than A. b. nevadensis. This does give the impression that they are singing a longer song.
Not only is canescens intermediate between belli and nevadensis in range and appearance, it also appears confusingly intermediate in song. Some songs, like the three below, closely resemble those of belli:
Songs of three individual canescens Sage Sparrows, Apollo Park, Lancaster, CA, 4/12/2011. Recordings by Walter Szeliga. The second bird sings twice on the recording below; cricket noise was edited out of the spectrogram.
Other recordings of canescens from farther north and east appear more similar to nevadensis song:
Song of canescens Sage Sparrow, Little Lake, California, 5/20/1956. Recording by William Fish (LNS 22855). Click to listen.
Here are a couple of recordings from within the breeding range of canescens in January and March, when migrant nevadensis can’t be ruled out:
Possible canescens Sage Sparrow song, Jawbone Canyon, CA, 1/11/2009. Recording by Andrew Spencer.Possible canescens Sage Sparrow song, 48 km north of Mojave, CA, 3/8/1989. Recording by Geoff Keller (LNS 44850). Click to listen.
Conclusion
While range, habitat and plumage may help identify many Sage Sparrow individuals to subspecies, there also appear to be useful differences in song. These song differences appear to be greatest between A. b. nevadensis and A. b. belli, with A. b. canescens forming a confusing intermediate group. It’s possible that song in canescens grades clinally from nevadensis-like songs in the northeastern part of its range to belli-like songs in the south and west. It’s equally possible that some of the nevadensis-like songs above actually belong to that subspecies instead of canescens.
On the whole, it seems that “classic” songs of nevadensis and belli are fairly easy to distinguish, but any Sage Sparrow singing an intermediate song may not be identifiable to subspecies by voice alone.
Blackpoll Warblers have among the highest pitched of all bird songs in North America. Most anyone who lives in the east (and can still hear it) should hear the loud “see-see-see-see-see…” of a Blackpoll at some point during spring migration. Listen to enough of them and you will doubtless notice a great deal of variation in the speed and particular note characteristic of the song.
However, there isn’t a whole lot of specific information in the field guides on the variability of Blackpoll Warbler songs. BNA does says of the speed: “Rate varies from 5 to 12 notes/s (Dunn and Garrett 1997), and frequency averages 8,900 hz (range 8,050–10,225 hz; Brand 1938; Fig. 3)” But it also says “No information on geographic variation”, and there is little other information on variation in Blackpoll Warbler song.
On my first trip to northern Coos County, New Hampshire (in 2008), I heard a very high pitched, very fast trill that I did not recognize. Upon tracking it down I was rather surprised to see it was a singing Blackpoll Warbler. I kept an ear out the rest of that day and found a half dozen or so Blackpoll Warblers, all singing that song. When I counted up how many notes per second the song contained I found that it was 19, well over the top end of the range mentioned in BNA. Upon mentioning this weird song type to a friend of mine from New Hampshire (Ben Griffith) he said that birders in the state were aware of this local dialect, and that all the birds up around Pittsburg, NH, sang like this, and none of the birds elsewhere in the state did.
This rather piqued my interest, so I’ve been keeping an ear out for singing Blackpolls ever since.
From what I’ve been able to find, my friend in NH is right about the very limited range of the super-fast song type. A few miles to the south, and even closer to the east, birds sing more normally paced songs (from Jefferson Notch, NH, and Saddleback Mt., ME, respectively). I have also heard many migrant Blackpolls at a number of locations from Ohio to Maine, and none of them sang fast songs like the NH birds.
Interestingly, a migrant bird recorded in E MA by Ian Davies (recording below) has a fast pitched song like the Coos birds. While it’s impossible to say for sure that this bird is from the Northern NH population, I would bet money that it is – E MA is directly south of these birds.
So if any of you hear Blackpoll Warblers regularly, or are heading to where you might, keep an ear out and let me know how fast they are singing…I’d be interested to know!
In 1989, the American Ornithologists’ Union split the Western Flycatcher into two species: Pacific-slope Flycatcher (Empidonax difficilis) and Cordilleran Flycatcher (Empidonax occidentalis), on the basis of vocal differences, differences in allozyme frequencies, and an area of sympatry in the Siskiyou region of northern California, where they were reported to mate assortatively.
Ever since then, these two species have been causing headaches for birders all across western North America. The conventional wisdom is that they are impossible to identify by plumage or structure, even in the hand. Voice is the only field mark.
Male position note
Most birders use only one clue to identify these two species: the subtle but distinct difference in the position notes of the males. Pacific-slope gives a one-syllabled upslurred whistle, and Cordilleran gives a two-syllabled upslurred whistle:
In “classic” examples like those above, note the distinct kink near the beginning of the Pacific-slope call, and the distinct break in the Cordilleran call (which can sometimes be rather indistinct, as it is in the second call on the right-hand spectrogram above).
However, the situation with these call notes is quite messy. For one thing, the calls are frequently variable within individual males, as in these examples:
Variable calls from a single male Pacific-slope Flycatcher, California Gulch, AZ, 5/13/2009.Variable calls from a single male Cordilleran Flycatcher, Larimer County, CO, 6/1/2007.
Some of the Pacific-slope examples above sound vaguely two-syllabled, and some of the Cordilleran examples sound distinctly one-syllabled. Here’s a more extreme version of the monosyllabic call type from a Cordilleran on territory in Colorado:
Cordilleran Flycatcher calls, monosyllabic variant, from a single male. Larimer County, CO, 6/20/2008.
Note the lack of the distinct kink on the spectrogram that is typical of Pacific-slope. That kink, however, makes little difference to the human ear, and birds that sound like this are likely to be identified as Pacific-slopes in the field.
I believe that’s what happened yesterday when a potential first state record Pacific-slope Flycatcher was reported yesterday in Gregory Canyon, here in Boulder, Colorado. I went to record the bird this morning, and captured a few of its calls on tape:
Cordilleran Flycatcher calls, monosyllabic variant, from a single male. Boulder, CO, 6/13/2011.
Dawn songs
Less well-known than the differences in position note are the differences in the male’s dawn song, which is usually given only before the sun rises. As with the position notes, the differences in dawn song are subtle and subject to both individual and regional variation.
Like the songs of Dusky and Hammond’s Flycatchers, the dawn songs of Pacific-slope and Cordilleran Flycatchers consist of three different phrases usually repeated in an “ABC” pattern:
Pacific-slope Flycatcher dawn song, Orange County, CA, 3/21/2009.Cordilleran Flycatcher dawn song, Larimer County, CO, 5/25/2008.
Compare each note of the songs:
In both species, the first element of the dawn song is a brief, high-pitched, simple whistle of variable inflection.
The second element is the loudest, longest, and most distinctive: in Pacific-slope it usually sounds vaguely two-parted (or at least split in the middle by a consonant), whereas in Cordilleran it usually sounds like a single slurred whistle. (Thus, the distinction in this case is the reverse of that in the position notes.)
In both species, the third song element is a clipped, lower-pitched, two-syllabled note; the second note tends to be higher than the first in Pacific-slope and vice versa in Cordilleran, but this difference is somewhat variable.
When I originally recorded the putative Pacific-slope Flycatcher in Gregory Canyon this morning, I thought I was hearing the standard Cordilleran dawn song from it in addition to its Pacific-slope-like position note. Upon examining the spectrograms of my recordings, however, it became clear that the bird singing the dawn song and the bird giving the position note were different individuals, since their vocalizations overlapped a number of times on the spectrogram. Thus, I do not believe that I heard dawn song from the Gregory Canyon bird this morning. However, I believe it can still be identified as a Cordilleran given the shape of its position note. Furthermore, I heard Cordilleran dawn song and Pacific-slope-like position notes from another individual male about half a mile farther up the canyon this morning.
On the whole, these two species, if they are indeed species, are exceedingly difficult to identify by ear. Spectrograms of the dawn songs or male position notes should be identifiable, however. Thus, decent recordings would be essential to document any occurrence of either species outside its normal breeding range.
Andrew Rush and Arch McCallum are currently researching these birds in great detail, so hopefully we will know much more about taxonomy and identification of “Western” Flycatchers in the next couple of years.
I’ve always been mystified by the breeding range of Bell’s Vireo. It inhabits three seemingly very different places — the dense deciduous tangles of the Great Plains, the mesquite thornscrub of southeastern Arizona, and the riparian chaparral of southern coastal California. Sure, they’ve all got lots of dense thickets, but so do lots of places in between.
As far as I can determine, the only other birds that occupy Bell’s Vireo’s entire range are continent-crawling generalists like House Finch and Mourning Dove that can be found practically everywhere. How can Bell’s Vireo be so forgiving of the differences between, say, a streamside plum thicket in South Dakota and a tangle of mesquite in the Arizona desert, without being able to tolerate the deciduous scrub of the Colorado foothills?
Part of the answer, of course, is that each of these habitats boasts a unique population of Bell’s Vireo with unique habitat preferences. Great Plains birds are the yellowish, greenish nominate subspecies; Arizona is home to the much less colorful subspecies arizonae; and coastal California hosts the endangered “Least” Bell’s Vireo,V. b. pusillus, the grayest of them all.
Recently, Elisabeth Ammon of the Great Basin Bird Observatory asked me for help in determining whether there are any vocal differences between pusillus and arizonae. During the upcoming breeding season, GBBO will be surveying sites in Death Valley National Park for Bell’s Vireo, including an area where the species was found last summer. If it is found to breed in Death Valley, the national park’s management plan may depend on whether the birds are determined to be of the federally endangered “Least” subspecies or the commoner arizonae.
The Sibley Guide to Birds says no vocal differences are known between the subspecies, but the recently revised Birds of North America account suggests otherwise:
Geographic Variation
Little known. A comparison of the samples taken from California and Arizona show slight differences in repertoire size, song length and number of notes per song…. Field researchers subjectively report qualitative differences in songs in different regions.
Unfortunately, BNA’s claims of vocal differences are backed up by very little quantitative information — only the observation that “Least” Bell’s Vireo has an average repertoire size of 9.2 songtypes per bird, whereas arizonae averages 10.6 songtypes. That’s a small difference indeed, one that means the repertoire sizes must necessarily overlap, and one that could even fall entirely within the margin of error. Even if further investigation confirms this average difference, it would be of zero use in field identification. And BNA says nothing further about differences in song length and number of notes per song. Thus, we’re left to investigate the most slippery category:
Qualitative differences
The initial prognosis for this blog post was grim, since the “Big Three” internet repositories of bird sounds – the Macaulay Library, the Borror Lab, and Xeno-Canto – contain precious few recordings of “Least” Bell’s Vireo. As of this writing, Macaulay and Borror lack them completely, and XC has only a few, all from Baja California Norte:
(There are two more possible Leasts on XC, from Baja California Sur and the Yolo Bypass in California, but I couldn’t confirm the subspecies in either case.)
YouTube to the rescue
Strange as it may seem, at the moment, YouTube actually contains more minutes of “Least” Bell’s Vireo song than the “Big Three” audio websites combined. Here are three definite “Leasts” (YouTube has at least one other possible/probable Least as well):
Update 4/2/2011: Matt Medler informs me that Macaulay actually does have several recordings of “Least” Bell’s Vireo [12345]! For some reason they were not originally visible to mortal eyes, but Matt has worked his magic, and now they appear when one searches the archive with the common name (“Bell’s Vireo”).
“Arizona” Bell’s Vireo
Now that you’ve wrapped your head around what the “Least” subspecies sounds like, check out these recordings of arizonae:
I’ve listened to all these recordings several times through, pored over spectrograms in Raven, and looked through Peter Beck’s 1996 thesis on the songs of “Least” Bell’s Vireo. Maybe there are some diagnosable differences in song, but I’ll be darned if I can find them. On current knowledge, the subspecies are indistinguishable by ear, and that’s the way it’ll stay for now.
Interestingly, there are a few differences in the calls from the different subspecies posted on Xeno-Canto, but I strongly suspect those are due to differences in the state of agitation of the individual birds, and not indicative of their genetic makeup. Sorry, Elisabeth — I got nothin’.
(If you got somethin’, please leave it in the comments!)
The Northern Pygmy-Owl is a fascinating bird for those of us interested in vocalizations and taxonomy. Many people think that what we call “Northern Pygmy-Owl” may contain somewhere between two and four species, based on regional differences in vocalizations. Here’s a brief overview of the differences, according to The Sibley Guide to Birds (2000), with a typical spectrogram and sound of each:
Pacific birds
According to Sibley, birds along the Pacific Coast of North America “give very slow single toots (1 note every 2 or more sec).” The example below is even slower than most; 2.5 seconds between notes seems pretty standard. Although one might expect birds in Montana to be part of the Interior West group, the sole recording available seems to fit better in this group.
Interior West group
Very few recordings of this group are available online (or anywhere else) — just two or three from Colorado [12] and one from Utah. They all seem to give single notes at very regular intervals, just over 1 second apart, totalling about 50 “toots” per minute when they’re going full-bore.
Mexican group (“Mountain” Pygmy-Owl)
Sibley says these birds “give mainly paired notes more rapidly (about 1 pair every sec).” Paired and single notes are usually mixed together, as on the recording below, and the paired notes are only slightly closer together than the single ones:
"Mountain" Pygmy-Owl (Glaucidium gnoma gnoma), Big Bend National Park, TX, 3/28/2008.
However, “Mountain” Pygmy-Owls also sometimes forgo the paired notes in favor of a rapid-fire string of single hoots almost identical to the song of the Northern Saw-whet Owl:
What we don’t know
What exactly is this Northern Pygmy-Owl saying? You could help us find out. Photo taken 11/4/2008 in Mission, BC by NechakoRiver (Creative Commons 2.0)
Nobody knows exactly where the changes between these songtypes occur, or how abrupt they are, because we just don’t have enough data. Most recordings of Northern Pygmy-Owl are of the highly vocal Mexican birds. As I mentioned above, very few recordings exist of the Interior West birds. There are none from potential areas of transition, like Idaho, Wyoming, northern Arizona, or New Mexico.
Now, my friend Arch McCallum is setting out to get to the bottom of this tricky situation — and you can help.
If you have access to Northern Pygmy-owls anywhere in their range this spring and summer, please do one of the following:
Find a singing pygmy-owl.
Get out a stopwatch and count how many “toots” the bird makes in one minute.
Send this information, along with location, date, and time of day, in an email to Arch (mccalluma AT appliedbioacoustics.com) or post it in the comments below.
If you wish, you can also make a one-minute audio recording. (Just take a video with your digital camera, or get a cheap voice recorder if you don’t already have the means.) Actually, if you wish, you’re welcome to record (or listen to) the bird for longer than a minute! The more data, the better.
Hope to see a lot of data points roll in this spring! Here’s to good owling.
What kind of swan is this? Are you sure? Ridgeway NWR, WA, 2/1/2009. Photo by SigmaEye (Creative Commons 2.0).
Trumpeter and Tundra Swans present a consistently underrated identification challenge in North America. Field guides and websites present a number of visual field marks, often with clear-cut illustrations or photos to show the differences — David Sibley presents a particularly good summary — but many of the differences are variable (like bill shape and color), change with the angle of viewing (like head shape), or are difficult to judge in the field (like size). Some of the best field marks, like the shape of the border between the facial feathers and the bill, may not help much in separating immature birds.
Many people think of swans as silent — ask them to imagine a swan and they will picture a species from Europe, the (somewhat) aptly-named Mute Swan, gliding serenely around a garden pond. It’s easy to forget that both native North American species were named for their vocalizations: “Trumpeter” and “Whistling” (as the New World subspecies of the Tundra Swan was known before it was lumped with the “Bewick’s” Swans of Siberia). As those very different appellations suggest, the two species sound quite distinct, and voice can be a good way to identify them.
At the same time, swans are vocally quite versatile (especially Tundra). I didn’t expect so much variety when I began my research, but then I never do. Variability aside, the bottom line is that vocalizations of Trumpeter and Tundra Swans consistently differ in pitch and tone quality with almost no overlap, and should thus be an excellent way to tell the species apart in the field.
Trumpeter Swan
Trumpeters sound remarkably low-pitched and nasal compared to Tundras — their call can easily be compared to the sound of a Red-breasted Nuthatch or (believe it or not) an Ivory-billed Woodpecker call — with many authors drawing comparisions to tin trumpets and taxi horns. The length and pattern of Trumpeter vocalizations is quite variable, and occasionally they can sound noisy (like in the last two calls on this recording). Typically, however, they sound much like this:
Note that on Tayler’s recording above, several of the calls include voice breaks, which are characteristic of large birds like waterfowl, hawks, and gulls, but would never be heard from the likes of a Red-breasted Nuthatch. The voice breaks contribute strongly to the tendency to describe these sounds as “trumpeting” or “bugling,” since voice breaks in bird sounds follow the same basic principle as changes between notes on a bugle (see this page for more information). Often, the voice breaks are lacking from Trumpeter calls.
Tundra Swan
Tundra’s voice is variable in pitch and pattern, but virtually always higher than Trumpeter, and much less nasal. Some authors compare it to the sound of Canada Goose, but in my experience the familiar honks of “Giant” Canadas are actually closer to Trumpeter calls. Tundra typically sounds much more like a Snow Goose, fairly high-pitched and rather mellow:
(Listen to the above starting at 3:40 on the recording)
Tundra Swans also apparently make some low moaning sounds, as attested by this recording at the Borror Library (probably a captive bird, given the location and the date):
Tundra Swan moan, Utah, 6/16/1973. Borror Laboratory of Bioacoustics #12361.
But the only sound I’ve found that might cause identification confusion is this occasional low-pitched, rough, nasal braying:
Tundra Swan braying, Alaska, 6/12/2006. Recording by Michael Andersen (LNS 133225).
(Listen to the above at the Macaulay Library, starting about 2:20 in the recording)
Of all the Tundra Swan vocalizations I’ve heard, this one sounds the most like a Trumpeter Swan. However, it may be given primarily on the Arctic breeding grounds, and usually appears interspersed with higher-pitched, more typical Tundra calls, so hopefully it shouldn’t cause too much confusion in the field.
For an excellent introduction to the variety of Tundra Swan calls, check out this recording by Gerrit Vyn of winter flocks approaching an evening roost in North Carolina. It’s nearly 50 minutes long, but it really gives a good sense of what you can expect Tundras to sound like in the field. (Note that some of the higher, hoarser calls on the recording may come from juveniles — but I don’t know enough about juvenile calls to say so with certainty. As always, there remains more to learn!)
Ian Cruickshank of Victoria, BC sent me a remarkable recording of a very confused Song Sparrow, which seems to be incorporating the complete song of a Northern Waterthrush into its own singing. Here’s the recording on Xeno-Canto:
When I first heard the recording, I thought the bird could be a juvenile using some imitations in its subsong — a decent possibility, given the late September date — but the comments Ian sent me about the recording seem to rule that out:
I first heard this Song Sparrow giving this song phrase in April of this year; I didn’t manage to record it at the time and it was a stroke of luck that I came across it again, engaged in a territorial match with another male Song Sparrow, belting out this song in the exact same location, in September this year. Obviously it’s a resident bird.
Let’s compare spectrograms. Here are a couple of excellent recordings of Northern Waterthrush songs. Note that waterthrushes, like Song Sparrows, have numerous song dialects across their range:
Here’s a spectrogram of one strophe of Ian’s weird Song Sparrow. Because the other birds on the recording make the spectrograms difficult to read, I’ve highlighted the Song Sparrow song in the background by coloring it red (a la The Sound Approach):
The last four (red) notes on the spectrogram are pure Song Sparrow, but boy, the rest of it sure looks like Northern Waterthrush, with the classic pattern of three contiguous series, including the rapidly downslurred whistles at the end. I think it’s highly likely that this Song Sparrow, during the “critical period” in which it was listening to the songs around it and piecing together its repertoire, mistook a Northern Waterthrush for a legitimate Song Sparrow tutor. This phenomenon is rare in Song Sparrows, but not unprecedented. Here’s what the Birds of North America account has to say about it:
Species displays innate preference for learning con-specific song and, like other Emberizidae, rarely mimics other species. Song Sparrows exposed to natural Song and Swamp Sparrow song in lab preferred strongly to learn conspecific song, but sometimes sang syllables of Swamp Sparrows (Marler and Peters 1987, 1988). Song Sparrows fostered by canaries (Carduelinae) did not mimic foster parents in one study (Mulligan 1966) but copied some elements in another (Kroodsma 1977). In contrast, Eberhardt and Baptista (1977) suggested Song Sparrows imitated Wrentit (Chamaea fasciata) syllables in wild, and Baptista (1988) recorded a Song Sparrow in San Francisco, CA, that produced White-crowned Sparrow song; another bird at Tioga Pass countersang White-crowned Sparrow song with neighbors of that species (M. Morton pers. comm. in Baptista and Catchpole 1989).
Song acquisition has been pretty well studied in Song Sparrows, and we know a lot about how they put together their repertoires. When they are raised in the laboratory with adult tutors of their own species, they usually tend to copy whole songs verbatim. They also prefer to copy the songs that are shared by multiple tutors — in other words, they seem predisposed to learn the most popular local tunes. However, some Song Sparrows act differently; one bird invented all its own songs, and several others tended to recombine elements from multiple tutor songs in creating their repertoire. Ian’s sparrow most likely did the latter: it was trying to invent a new Song Sparrow song using elements of other Song Sparrow songs it had heard, but it misidentified one of its tutors and ended up with a weird, chimeric melody.
Now that it is an adult bird, it’s likely to sing this hybrid songtype for the rest of its life. It’s hard to say whether that will disadvantage it. Various studies have measured Song Sparrows’ responses to abnormal songs (including, among others, artificially constructed songs that arranged Swamp Sparrow syllables according to Song Sparrow syntax, and vice versa), and the findings tend to agree that imitations or corruptions of Song Sparrow songs elicit weaker responses than typical songs, but they still elicit responses. Thus, this abnormal song likely won’t be as effective in driving away a rival male or attracting a female mate, but it may get the job done. If, like most Song Sparrows, this individual has between 5 and 13 different songtypes in its repertoire, then the weird waterthrush-song might only be deployed between 8% and 20% of the time. Assuming it’s the only abnormal songtype in the repertoire, it might not prove a huge disadvantage to the singer.
If this bird maintains a territory over multiple years, there’s a chance that juvenile Song Sparrows moving into nearby territories might even select it as a tutor, adding some or all of the Northern Waterthrush syllables to their own songs second-hand and potentially propelling them into the local Song Sparrow vernacular in the long term. A similar process might explain why, for example, so many of the “Thick-billed” Fox Sparrows in the Sierra Nevada end their song phrases with what appears to be a straightforward imitation of the “kleer” call of Northern Flicker:
However, I think this unlikely to happen among Vancouver Island Song Sparrows. Song Sparrows seem much less likely to imitate than Fox Sparrows, which means Songs probably have a stronger (though not ironclad) genetic mechanism to guide young birds to ignore the syllables of other species and incorporate only their own. My prediction: this wrong-singing sparrow might not be a complete pariah, but in the long run he probably won’t prove a strong competitor for territories and mates either, and his borrowed syllables are unlikely to impress the next generation to follow in his footsteps. He’s a slightly socially inappropriate, oddball schmo: the George Costanza of Song Sparrows. We’ll call him George for short.
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”:
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.
