I don’t mean “pub” as in “place to buy a drink.” I mean “pub” as in “publication!” The western volume of the Peterson Field Guide to Bird Sounds hits store shelves and ships from online retailers today! (Maybe a celebration at the local pub is in order.)
Tonight’s book signing at the Front Range Birding Company in Boulder is full — we’ve had RSVPs for all available seats. I’ll be doing another signing at the Littleton location of Front Range Birding Company next Wednesday, April 10, 6:30 – 9:30 PM.
Here are some of the places I’ll be speaking and selling books this year. If I’ll be in your area, come out and see me! If I’m not scheduled to be in your area, contact your local Audubon society or birding festival and suggest that they book me!
Wednesday, April 10, 2019 – Littleton, Colorado
“The Language of Birds” and book signing, Front Range Birding Company, 10146 W. San Juan Way, Unit 110, 6:30 – 9:30 PM
April 11-13, 2019 – Las Vegas, Nevada
“The Amazing Sounds of Birds,” Nevada State College, Thursday, April 11
“The Language of Birds,” Red Rock Audubon Chapter Meeting, Saturday, April 13
Monday, April 22, 2019 – Denver, Colorado
“The Secret Lives of Ducks,” Denver Field Ornithologists Meeting, 7:00 PM, Unity Spiritual Center Denver, 3021 S. University, Denver
May 3-5, 2019 – Keosaqua, Iowa
Iowa Field Ornithologists Spring Meeting: Keynote speaker and workshop leader
May 10-12, 2019 – Moses Lake, Washington
Washington Ornithological Society Spring Meeting: Keynote speaker and workshop leader
Saturday, May 18, 2019 – Colorado Springs, Colorado
Pikes Peak Birding Festival – Bird Sounds field trip and book signing
June 1-2, 2019 – Portland, Oregon
Oregon Birding Association Annual Meeting, Kennedy School McMenamins, NE Portland: Keynote speaker and workshop leader
June 13-17 – Montrose, Colorado
Colorado Field Ornithologists Convention: Keynote speaker and workshop leader
August 21-25 – Albuquerque, New Mexico
Western Field Ornithologists Convention: Sound ID Challenge moderator and workshop leader
September 13-15 – Kingston, New York
New York State Ornithological Association Annual Meeting, Catskill Center for Conservation and Development: Keynote speaker
November 20-21 – Stockton, California
Central Valley Birding Symposium: Keynote speaker and workshop leader
Today, my own advance copies of the Peterson Field Guide to Bird Sounds of Western North America were finally delivered to my door. What a thrill to hold it in my hands at last! I started work on this project in 2003, so this moment has been 16 years in the making.
Official publication date is April 2, which is when it will hit store shelves and ship from online retailers. If you’re in the Denver metro area, we’ll be having a launch party and book signing at the Front Range Birding Company in Boulder on Tuesday, April 2, 6:30 – 9:30 PM. I’ll be doing another signing at the Littleton location of Front Range Birding Company on Wednesday, April 10, 6:30 – 9:30 PM. At both events I’ll be giving a presentation titled “The Language of Birds” in addition to signing copies of the book, which will be on sale.
All the sound files from western North America have been added to the website that accompanies the book: petersonbirdsounds.com. There are now over 7,500 sound files on the site, all of which can be streamed online for free, with a real-time scrolling spectrogram. No purchase of the book is necessary. I believe it is the most complete and best curated collection of bird sounds currently available for North America.
I’ll be traveling a lot this year for book promotion, so come see me if one of my upcoming events is in your area! If you are interested in having me come speak to your group, drop me a line! I can speak on a variety of topics, and am developing new talks all the time.
Thank you to everybody who helped make the Peterson Field Guide to Bird Sounds a reality. I couldn’t have done it without all of you who shared your media, your expertise, and your enthusiasm for this project.
One question I get over and over again is: which apps work best if you want to make spectrograms on your phone? I’ve got a couple of recommendations. (Note: I have no financial interest in any spectrogram app.)
Why use a spectrogram app?
Spectrogram apps are terrific because they can allow you to make a picture of a sound right when you hear it. If you are trying to identify bird sounds, a spectrogram app can show you the shape of the sound, and then you can compare that shape to the ones in the Peterson Field Guide to Bird Sounds to find a match. It turns bird sound identification into a visual challenge, which can be really advantageous since many of us have an easier time remembering visuals than sounds.
What should I look for in a spectrogram app?
There are a lot of apps out there that will generate spectrograms. If you are interested in bird sounds, here are the main features to look for:
The top of your display should be around 10,000 Hz (= 10 kHz). This is roughly the average upper limit of hearing in many adult humans, and it’s roughly the upper limit of most bird sounds too. If your app doesn’t top out around 10,000 Hz, look for the option to change “sample rate” or “sample frequency.” The top frequency on the display will be half the sample rate. Thus, a sample rate of 22,000 or 24,000 Hz should generate a display that is around the optimum height for bird sounds.
The display should scroll across about an inch of screen per second. Most apps don’t scroll this fast, so just look for one that has the fastest possible speed. If the scroll moves too slowly, the bird sounds will end up looking horizontally squished, and it will be hard to see the necessary detail.
The display should have a black-on-white option. The default is usually multicolor-on-black, which is not ideal. Grayscale-on-white is much easier to read, because the sound is the signal; it is the text. Text should always be dark-on-white for extended reading.
The display should scroll, not wrap. That is, the whole spectrogram should move across your screen from right to left, with the most recent sounds at the right.
You should be able to pause and screenshot the display. This allows you to “take pictures” and save them for later viewing.
You should be able to play back the recorded sound later. Even the worst-quality phone recordings are usually higher in resolution than phone spectrograms, so recording the sound is highly recommended.
So… which apps do I recommend, as of February 2019?
For iPhone: SpectrumView
SpectrumView for iPhone is great because it has all the above features in the free version. I don’t own an iPhone so I haven’t used it myself, but it’s highly rated and from what I can tell, does a very nice job of illustrating bird sounds.
For Android: SpectralPro Analyzer
On my Android phone, I use SpectralPro Analyzer by RadonSoft. It’s not as good as SpectrumView, but it’s the best I’ve been able to find for Android. The two big drawbacks are: 1) that it does not record audio; and 2) that key features are only available in the paid version. Last I checked the paid version was only about $5. And to work around the lack of recording ability, you can always download a separate free audio recording app and run it at the same time as SpectralPro. That’s a little clunky, but it does the job.
If you are aware of any app that can do better than the ones I’ve listed, let me know!
Only one study on the vocalizations of Purple Martin has ever been published, by swallow guru Charles Brown in 1984. In that study, Brown compared the sounds of Purple Martins at two sites: one in central Texas, and one at high elevation in the Chiricahua Mountains of southeast Arizona. He reported differences between eastern and western birds in several types of vocalizations, as summarized here:
West
East
Veer
Downslurred
Slightly upslurred
Veer Phrases
Almost always include a stereotyped 3-note pattern
“Uttered in variable sequences […] with no pattern”
Burrt
Long (0.3 – 0.6 sec), consecutive calls often run together
Short (0.1 – 0.2 sec), consecutive calls usually well separated
Day song (male)
Long (2 – 6 sec), with at least 2-3 grating sounds interspersed
Short (1.5 – 3 sec), with grating sounds only at the end, if present
Female song
More downslurred syllables than Burrts
More Burrts than downslurred syllables
Since Brown’s study was conducted at only two sites, I’m curious whether the findings can be generalized across the continent. Do all eastern birds sound like the ones at the site in Texas? Do all western birds sound like the ones at the site in Arizona? Or do Purple Martins show patterns of regional variation all across North America?
Let’s check some of these reported differences against available recordings.
Veer and Veer Phrases
Brown didn’t distinguish between the Veer and the Veer Phrase; he discussed them together under the name “zweet calls.” When he said “zweet calls” of eastern birds tend to be slightly upslurred, I suspect he was referring to Veer Phrases instead of individual Veer calls, because the individual Veer calls are generally downslurred all across the species’ range:
This recording from the southwestern desert (ssp. hesperis) sounds different–shorter, sharper, and less burry.
But not all hesperis sound this way. These sound the same as eastern birds:
So that short, sharp version from Arizona might actually represent something other than the Veer calls — perhaps an intergrade between Veer and Tew calls.
Day Song (male)
In this recording from Tucson (presumably of hesperis, the desert subspecies), the song matches Brown’s description for western birds, with multiple grating sounds throughout the song (only properly heard once, at 0:33):
Same goes for this song from Humboldt County, California (at 0:26):
And this recording from the high Chiricahuas (from 0:45 to the end):
So it seems that at least some birds all across the continent give multiple grates in their songs; some birds everywhere give a single grate at the end; and some birds everywhere leave out grates entirely.
Overall, I’m not seeing much support for the idea of systematic vocal differences between eastern and western populations of Purple Martins. There are certainly regional and individual differences, and probably local dialects, as would be expected in almost any bird that learns its song. But I’m always willing to learn more, and if you can enlighten me on this topic, please do!
On the xeno-canto forum, people frequently post unidentified bird sounds from all around the world. I can’t be of much help on the mysteries from Europe or Africa or India, but if I see an unidentified sound posted from North America, I check to see if it’s something I recognize.
Last year Bates Estabrooks uploaded an odd call he’d recorded in Tennessee. It didn’t exactly resemble anything I’d heard before, but I told him it was probably a Tufted Titmouse. Several other people on the forum thread agreed. Here’s the sound:
Bates wrote back with a perfectly legitimate question: what made it a Tufted Titmouse? If it didn’t exactly resemble anything I’d heard before, how could I be sure?
Here’s what I told him:
It’s simultaneously pretty simple, and frustratingly difficult. Here’s the reasoning I used:
It’s very high-pitched (almost entirely above 6 kHz).
It’s medium-complex (2-syllabled).
I’ve never heard anything quite like it (i.e., it doesn’t fit for any of the other birds that regularly give very high, 2-syllabled calls, like Brown Creeper or Golden-crowned Kinglet).
“I’ve never heard anything quite like it” is actually an excellent field mark for Tufted Titmouse (and a couple other species, such as Blue Jay). The frustrating part is that it takes time to get to the level of experience where this field mark is helpful.
When it comes to identifying bird sounds, unfamiliarity can actually be a very useful mark. Of course, it becomes more useful as you learn more bird sounds (and can therefore rule them out). The legendary Ted Parker knew almost all the bird sounds in the Western Hemisphere — so when he heard something unfamiliar in a tape from Bolivia, he postulated that it must be a species new to science (and it appears he was probably correct). Most of us are never going to arrive at this level, of course.
Unfamiliarity can be a visual field mark too. Never seen a hawk quite like it before? It’s probably a Red-tail. (Photo by Steve Jurvetson)
Note that I’m not talking about unpredictability, which is a field mark for mockingbirds, thrashers, catbirds, or Yellow-breasted Chats. Unpredictability is different from unfamiliarity. Unpredictable birds might sing unfamiliar notes or phrases, but then they quickly move on to another type of sound. I’m talking about birds that repeat the same unfamiliar sound over and over.
When I was a young birder in eastern South Dakota, I soon realized that most weird, unfamiliar bird sounds came from Northern Cardinals. When I moved to Massachusetts for college, I learned to bet on Tufted Titmouse as the source of a wacky sound. In graduate school in western Oregon, the vocal tricksters were Hutton’s Vireo and Bewick’s Wren. And of course, two other consistently unfamiliar birds are Blue Jay (especially in the wide variety of so-called “pumphandle calls“) and Red-winged Blackbird (especially the many whistled variations of the alert calls).
I’m curious about other people’s experiences. What birds have you learned to identify by their unfamiliarity?
Last Thursday I talked about the book with Mark Lynch of WICN – you can hear that interview online. Tomorrow morning (Sunday March 5), I’ll be interviewed live on Ray Brown’s show Talkin’ Birds, which is syndicated all over New England! Listen in at 9:30 AM Eastern.
I will be doing a lot of traveling this year to promote the book! Check my current list of events to see if you can catch me in your area. If you’d like me to speak to your group, just send me an email!
Black Guillemot in “hunch-whistle” posture, Moville, Ireland, 5/22/2007. Photo by Sean Mack (CC 2.0).
“No differences known,” says the Sibley guide about the voices of Black and Pigeon Guillemots.
This isn’t quite true. But the differences certainly are not widely known. Since these two species are impossible to mistake for other alcids either visually or vocally, and because they barely overlap in range, most birders have neither the opportunity nor the incentive to listen for vocal differences between them. But the differences are quite striking when you know what to listen for.
Each guillemot species has two types of long, complex vocalization, along with some shorter calls. The long, complex vocalizations are rather plastic and grade into one another within each species.
“Songs”
It’s an open question whether the term “song” is appropriate for any guillemot vocalizations, but for now, I’m using it to describe the most complex and most stereotyped sound in each species’ repertoire, often given from the nest. In both Black and Pigeon Guillemots the main part of the “Song” is usually preceded by a high, rapid series of chip-like notes. Black Guillemot follows up with a series of couplets that can recall the “squeaky wheel” song of Black-and-white Warbler. Sometimes this is followed by chip-like notes again. In Pigeon Guillemot, by contrast, the initial chips culminate in a single longer whistle and then a fast, slightly falling trill:
Black Guillemot Song, Meat Cove, Nova Scotia, 6/27/2007 (LNS 133325; click image to listen. Spectrogram is from the tenth minute)
Overall, Pigeon Guillemot’s song is much faster. Black Guillemot rarely, if ever, gives a series of notes fast enough to be called a trill.
Seet Series (“Hunch-whistles”)
In addition to what I’ve called song, both species of guillemots give another longer but simpler vocalization that may have a more aggressive function, and which is usually given in a “hunched” posture like that shown in the photo above. (“Songs” can be given in a somewhat similar posture.)
In Black Guillemot, the Seet Series or “hunch-whistle” is a series of very high couplets again reminiscent of a Black-and-white Warbler’s “squeaky wheel” song, except that in the guillemot it is slower and goes on much longer, sometimes for 30+ seconds, gradually rising and falling in pitch. The equivalent sound in Pigeon Guillemot is much slower, alternating series of short “psip” notes with series of longer whistles.
Black Guillemot Seet Series, Cape Bonavista, Newfoundland, 7/5/2007 (LNS 133369; click image to listen).
Pigeon Guillemot Seet Series, Carmel, California, 6/26/1961 (LNS 3856; click to listen. Spectrogram is from the fifth minute).
Black Guillemot’s vocalizations are much more likely to involve series of couplets with alternating notes, often in a long-short, long-short pattern. Pigeon Guillemot’s vocalizations rarely involve long-short couplets for any continuing length of time; they are much more likely to contain the same kinds of notes repeated several times before switching to a new kind of note. However, vocalizations in both species are highly plastic.
“Seer” calls
The most commonly heard call from both species of guillemot is a high-pitched, finely buzzy “Seer” that may recall a Cedar Waxwing. These calls are rather plastic, but usually slightly downslurred. They seem to average higher-pitched in Pigeon Guillemot, but are otherwise almost the same.
Black Guillemot “Seer” calls, Cape Pierce, Nova Scotia, 6/28/2007 (LNS 133380; click image to listen).
Pigeon Guillemot “Seer” call, St. Lazaria Island, Alaska, 6/17/2007 (LNS 136454; click to listen).
Both species can also give shorter high-pitched notes, ranging from “seeps” or “pseeps: to quick sharp chips.
Even though birders in the field are not particularly likely to need to know the vocal differences between the guillemot species, I hope you find this information enlightening. Personally, I find the sounds to be a fascinating glimpse into the evolution and taxonomy of these charismatic birds!
The waterfall (cascada) in Parque Natural Mexiquillo, Durango, Mexico. Photo by Roberto González (CC-BY-2.0).
We were excited to arrive at Parque Natural Mexiquillo before the break of dawn in June. This underappreciated park is right on one of Mexico’s most celebrated birding routes, the Durango Highway — but it is an hour or two farther east than the Tufted Jay Preserve, and much less frequently visited. The drier forests of Mexiquillo host a noticeably different avifauna than the wetter areas closer to the coast. Mexiquillo is more likely to produce birds typical of the dry “sky islands” of southern Arizona: Buff-breasted Flycatcher, Western Bluebird, Plumbeous Vireo, and even American Robin. It’s much better habitat for the likes of “Type 6” Red Crossbills (which we recorded) and Eared Quetzals (which we did not find). Of course, it also has Red Warblers, Elegant Euphonias, and Rufous-capped Brush-Finches.
And it has a waterfall.
This is particularly noteworthy because the mountains of west Mexico are high and dry — and not much water means not many waterfalls. Which means not many places to look for waterfall-loving swifts.
We were very interested to see what kinds of swifts would be flying around the waterfall at daybreak. A report from 2013 had us wondering whether this would be a good place to record Black Swifts, and a tantalizing recording from Chihuahua had us wondering whether something super-rare might be lurking under the cascada (and under the radar), like the “avian unicorn” White-fronted Swift (Cypseloides storeri).
When we first arrived, before first light, all was quiet, except for the roaring water and the aerial singing of Violet-green Swallows. Off in the distance, a Spotted Owl hooted. No swifts. Soon a dawn-singing Pine Flycatcher became a serious distraction. By the time the sun was fully up, we were totally engaged in all the other wonderful birds in the park, and we had completely given up on the swifts. Until suddenly, something dark swooped by overhead with a sound like the crackling of electrical wires. Chestnut-collared Swift!
Then another group of swifts flew by, and I heard a sound familiar from the mountains of Colorado: Black Swift.
For the next hour, these two species swirled over our heads, sometimes swinging pretty low. The encounter was simultaneously a letdown and a thrill. On the one hand, it woke us up from the pipe dream of documenting some ultra-rare Cypseloides vocalizations. On the other hand, it was a terrific opportunity to spend time with two species that it can be awfully hard to see and hear well. It cleared up a long-standing mystery about whether the Black Swifts of Mexico might sound different from the ones farther north (answer: they don’t). And it gave us the field experience necessary to help identify the Chihuahua mystery swift as the first Chestnut-collared documented in that state. One key takeaway: Black and Chestnut-collared Swifts can look astonishingly similar, even when you get good, prolonged looks. But by sound, they can be separated right away.
While I concentrated more on the audio recording, Andrew was able to get some decent flight shots of the Black Swifts:
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
Black Swift, Parque Natural Mexiquillo, 6/4/2015. Copyright Andrew Spencer
We were hoping to figure out whether the Black Swifts of Mexiquillo belonged to the northern subspecies niger, which breeds in the United States and Canada, or the southern subspecies costaricensis, which breeds in — you guessed it — Costa Rica. The birds in Mexico have been attributed to each of these subspecies by different authors. The Mexiquillo Black Swifts were surprisingly well marked, some with bright white foreheads, some with extensive white scalloping below. So we thought this might be a mark for costaricensis. But when Andrew reviewed and photographed Black Swift specimens in the Harvard collection earlier this week, he found it nearly impossible to separate the subspecies by coloration. The size difference is noticeable on the specimen table, but is subtle enough that it would be virtually useless in the field.
Dorsal view of female Black Swifts, from British Columbia (niger, at left) and Costa Rica (costaricensis, at right).
Ventral view of female Black Swifts, from British Columbia (niger, at left) and Costa Rica (costaricensis, at right).
Frontal view of female Black Swifts, from British Columbia (niger, top row) and Costa Rica (costaricensis, bottom row).
Dorsal view of male Black Swifts, from British Columbia (niger, at left) and Costa Rica (costaricensis, at right).
Ventral view of male Black Swifts, from British Columbia (niger, at left) and Costa Rica (costaricensis, at right).
Frontal view of male Black Swifts, from British Columbia (niger, top row) and Costa Rica (costaricensis, bottom row).
So, the subspecies of the Durango birds remains a bit of a mystery. Any comments or discussion would be appreciated!
(Guest post by Ted Floyd, editor of Birding magazine and bird sound enthusiast)
Fish swim, snakes slither, songbirds sing. Okay, some songbirds’ songs aren’t especially songful: The “song” of the Cactus Wren sounds like an old car starting up, for example, and the “song” of the Yellow-headed Blackbird sounds like someone being strangulated. Nevertheless, the chugging of the wren and the tormented gasping of the blackbird qualify as song, pretty much any ornithologist will tell you.
But some songbirds actually are believed not to sing. Probably the best known example in the U.S. is the Cedar Waxwing. Oh, they’re plenty noisy, flocks of them trilling and lisping and wheezing their way from tree to tree. But they don’t actually sing, it is said. I can see why. I mean, they’re so over-the-top gorgeous, with their waxy wingtips, wispy crests, and just general, well, gorgeousness. One look at a Cedar Waxwing, and it’s love at first sight—whether you’re a human or a waxwing. No need for song.
Less well known is that Bushtits are said not to sing. Like waxwings, Bushtits roam about in noisy flocks. But they’re drab, they’re tiny, they’re not as widespread in the U.S. as Cedar Waxwings, and much of their range comprises hot, arid, rocky, low-diversity shrublands eschewed by many birders. Out of sight (and out of earshot), out of mind.
—–
Of late, I’ve had occasion to question the conventional wisdom that Bushtits do not sing. Here’s the deal: In just the past couple years, Bushtits have invaded my suburban neighborhood near Denver, Colorado. Suddenly, Bushtits are everywhere. There’s a certain novelty for me about seeing and hearing Bushtits. I find myself paying special attention to Bushtits.
In particular, I’ve noticed that one Bushtit vocalization—a short, high-pitched trill—tends to be given by solitary birds or by birds in pairs. Yes, this vocalization can be heard from birds in large flocks and at any time of the year; in the same way, the Red-winged Blackbird’s classic song may be heard in huge roosts on the wintering grounds. I can see from my field notes, as well as from my comments posted to Xeno-Canto, that I’ve been wondering for a while if this short, high-pitched trill functions as the song of the supposedly songless Bushtit. And I had an experience the other day that really got me thinking.
—–
Friday, March 6, 2015, was the first sort-of warm day we’d had around here in a while. Even through my closed window, I could hear House Finches singing their twangy warbles and collared-doves chanting “eighteen” in Greek. (Every wondered why they’re called decaocto?) I could also hear the trilling of a Bushtit, so I went outside to investigate. A Bushtit was teed up on a branch in my yard, vocalizing away. I went back into the house, got my recorder, and came back outside again. The bird was still at the same perch and still vocalizing, and I recorded it. Then I did something absurd.
The male Bushtit apparently singing, Boulder County, CO, 3/6/2015. Photo by Ted Floyd
I went back inside, looked for my scope, and looked for my cell phone. I found them, gathered them up, and went back outside. The Bushtit was still there, still vocalizing. I set up the scope, fired up the phone, fiddled with various settings, and got a bunch of photos. That’s absurd! Bushtits aren’t supposed to stay put for ten minutes, as this bird did. They’re not supposed to stay put for ten milliseconds.
But this guy (confirmed as a male by the digiscoped images) was at his perch, teed up, constantly giving the same vocalization. And when I reviewed the soundfiles, I saw something I hadn’t consciously noted while with the bird in real life: Another Bushtit, quite some distance away, was counter-vocalizing with the bird in my yard.
So we’ve got a bird perched for ten-plus minutes, delivering the same vocalization over and over again; the bird’s a male; it’s a sunny and sort-of warm morning in early spring; and another bird is dueting with it. If these were cardinals or chickadees, we’d unquestioningly say they were singing.
But were the Bushtits “really” singing?
The literature says Bushtits don’t sing. I checked Sarah A. Sloane’s BNA account [subscription required], which states: “There is no song in the usual sense. The closest Bushtits get to a song is the somewhat musical, but apparently unstructured, ‘twitterings’ given by many individuals simultaneously when in a close group.” The sprawling account by Arthur Cleveland Bent doesn’t treat song, best I can tell. And a detailed 1903 treatise by Joseph Grinnell likewise contains no mention of song.
Were the Bushtits “really” singing? I think we need first to address another question: What is birdsong? Immediately, I’m reminded of the famous quip by U.S. Supreme Court justice Potter Stewart: “I know it when I see it.” (Or, in the case of birdsong, hear it.) That’s good enough for jurisprudence perhaps, but inadequate for biology. David A. Spector took up the matter in a 1994 paper in the Journal of Theoretical Biology: “Definition in Biology: The Case of ‘Bird Song.’ ” The problem is that different authorities have different definitions, many of them intrinsically circular.
—–
I’m a scientist by training, but more a philosopher by temperament. I get it, at a scientific level, that the matter of song in the Bushtit is unresolved. It remains to be proved that the male Bushtit’s short, high trill functions as song. I’ve stated a hypothesis; now someone needs to go out and test it.
But I’m temperamentally a philosopher, I said, and I can’t resist ending on that note. The morning after my encounter with the provisionally singing Bushtits, I came upon a Black-capped Chickadee up on a branch. The bird was vocalizing. So was another chickadee, farther away. I made a quick-and-dirty recording; you can clearly hear one bird and sort of hear the other bird, and they’re inarguably singing—singing one of the best known and most beloved songs of any bird in the U.S.
Common Raven, Bryce Canyon National Park, Utah. Photo by National Park Service (public domain).
Every once in a while, somebody will put together a list of underappreciated identification challenges among North American birds. Common and Chihuahuan Ravens always make the list.
Here in Colorado, we have lots of ravens. Conventional wisdom says the ones on the southeastern plains are Chihuahuans, and the rest are Commons. But not everyone accepts the conventional wisdom. Some believe that Chihuahuan Ravens are not only the default raven in the southeast, but also regular wanderers north to the Wyoming border. Others maintain that to find a real Chihuahuan Raven, you have to go south of Colorado altogether.
For a long time, I haven’t been sure what to believe. But I’ve been browsing my own audio collections and those online, and I’m starting to think that voice is actually a very good character — maybe the best field character — for separating these two species. I’m willing to be convinced otherwise, and I’m interested in hearing from anybody who has experience with these two birds. But at the moment, here’s what I think I know about the sounds.
Chihuahuan Raven
It seems to me that Chihuahuan Raven may actually have one of the most predictable (least variable) voices of any North American corvid. Its classic call is a harsh “caw” that is deeper and much more coarsely burry than most “caws” of American Crow. It is of medium pitch, slightly nasal, and barely upslurred. It actually has something of a quacking quality — reminiscent of the harsh-sounding quacks that female Mallards do when they’re agitated.
Once you start comparing multiple recordings, this call of Chihuahuan Raven starts to seem remarkably consistent rangewide and from bird to bird:
Occasionally a couple of the birds in these recordings switch to some similar but slightly higher-pitched calls. And females will also do the clucking gurgles that many female corvids do (you can hear some on my recording above from Chihuahua). Other than that, though, these six examples are all so similar that they could almost be from the same individual bird.
Common Raven
From one of the least variable North American corvids, we transition to one of the most variable.
I’ve seen a number of sources argue that Chihuahuan Raven averages higher-pitched than Common Raven. This is a really problematic statement. It’s true that if you hear any really low croaks, you can be sure they’re from a Common:
But if you hear any really high croaks, you know they’re also from a Common:
(The ravens in that Red Top Ranch recording, by the way, were flying in a loose flock of 5 over featureless shortgrass prairie in southeast Colorado — location, habitat, and behavior all suggesting Chihuahuan Raven. But the voice doesn’t seem to match.)
Common Raven runs the gamut of possible pitches and tone qualities, from far below Chihuahuan’s pitch range to far above it. Chihuahuan occupies a limited space in the middle. Not only are Commons variable, but they often change sounds while you’re listening to them, unlike Chihuahuans. I might go so far as to say that if you hear a group of ravens giving a whole bunch of different-sounding calls, you’re almost certainly listening to Commons:
Some recordings of Common Raven come pretty close to matching the typical call of Chihuahuan Raven, but exact matches seem to be rare. Interestingly, the most Chihuahuan-sounding Commons I’ve found are mostly from California:
You may recall that over a decade ago, Common Ravens in California were found to be genetically distinct from other Common Raven populations — more closely related to Chihuahuan Ravens than to other Commons. So should we split Common Raven? Or reclassify California’s ravens as Chihuahuan?
Well, maybe not. The study found that Chihuahuan Raven and “California” Common Raven were still pretty distinct genetically. And more recent followup research has showed that “northern” Common Ravens and “California” Common Ravens have apparently been interbreeding extensively in western North America for a very long time, and the genetic differences between them may be decreasing over time. You could make a case for lumping ALL of North America’s ravens into one species, but I’m not sure that’s warranted, especially if Chihuahuans and Commons are not regularly interbreeding. More studies will need to be done on that.
On the whole, I could be underestimating the vocal variation in Chihuahuan Raven. And maybe there’s a lot of interbreeding going on in places like southeast Colorado. But at the moment, it really looks to me like Chihuahuan is a very predictable-sounding bird. And if it is, then vocalizations may be the single best way to identify one in the field.
