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Category: Identification

That’s No Starling

That’s No Starling

I have a confession to make.

For six years now, after my morning commute, I have parked below Folsom Field, the football stadium of the University of Colorado, and walked around the edge of it on my way to my office.  Frequently, I used to hear this odd bird singing from somewhere up on or near the roof of the stadium:

I could  never see the bird; it always sounded echoey, like it was inside the roof of the building.  Sometimes it would sing in the mornings, but more often it would sing at night — sometimes all night, as far as I could tell.  Fall, winter, spring, no matter: the unseen singer was belting it out.

The bird sang in bouts consisting of series of notes; it had at least eight different note types, many of which sounded screechy, and some of which were dead on for European Starling.  Some of its note types sounded like mimicry — of birds like American Kestrel, Cooper’s Hawk, and Red-shouldered Hawk — which also pointed to starling, as did the singer’s habitat (the roof of a building in a predominately urban environment) and its insomnia.

So I just figured it was the “night song” of the starling, and I figured everybody knew about it.

This fall, I heard those crazy nocturnal sounds again, this time from atop the Boulder Bookstore in downtown Boulder.  I recorded it and made spectrograms, and then I set off to the scientific literature to find out what kind of starling song it was.

It turned out nobody had ever recorded anything similar from a starling.

For a little while I started to get excited.  Was I the first to realize that starlings’ night songs were different from their day songs?  How could science have missed this?  Starlings are abundant, they live in cities, they’re noisy as heck, and they’ve been studied like few other bird species!  Was there a whole new starling repertoire being sung right under everybody’s noses?

You guessed it, I was being stupid.  Tayler Brooks cleared up the confusion for me.

birdxpeller-proI was fooled by one of those electronic loudspeaker devices that they put on rooftops to scare away birds.  According to the Bird-X Company, the BirdXPeller Pro “automatically broadcasts a variety of naturally recorded bird distress signals and predator calls to frighten, confuse, and disorient birds.”  No wonder it sounded like a distressed starling…and then like a kestrel and a Cooper’s Hawk and a Red-shouldered Hawk.  No wonder it was singing at night from the tops of buildings.  Sigh.

Now that we’ve had our little identification lesson for today, I want to ask this question of all the birders out there.  Is the BirdXPeller Pro actually likely to work?  According to the Ontario Ministry of Agriculture, this type of repellent device is “only effective against the bird species whose distress calls are encoded on the microchip.”  I find that difficult to square with Bird-X’s claim that the BirdXPeller Pro will repel not only starlings, grackles and sparrows, but also “seagulls,” cormorants, and, yes, vultures.

Frankly, I tend to think that most birds are smart enough not to be fooled by the same old playback over and over, even if it is a conspecific distress call.  Then again, perhaps the Bird-X company is craftier than I’m giving them credit for.  They’ve certainly sold a bunch of these devices, enough to warrant a caution to earbirders.

But…vultures?

Pacific Wren, Part Two

Pacific Wren, Part Two

It was a wet and foggy day in April.  I was standing in a damp little nook in dense woods, long before the first leaves would even think about opening, weeks before most migrating birds would get within a thousand miles of southeast South Dakota, listening to a cascade of musical notes that seemed like it would never end.  It was echoing off the trees and the mossy banks, coming from somewhere tantalizingly close — but from exactly where, I couldn’t for the life of me figure out.  After I stood there for perhaps ten minutes, I finally spotted it: a tiny brown bird singing from a pile of leafless brush, fifteen feet in front of me in plain sight.  My first Winter Wren.

By some strange coincidence, the details of that experience almost perfectly match the details of my first encounter with Pacific Wren, when, on another wet and foggy day in April, I spent another ten minutes trying to find the amazing vocalist hidden among the dense, damp vegetation, this time on the slopes of Skinner Butte in Eugene, Oregon.  At the time I had little idea I was seeing a different bird than the one I knew from the east.  The song was familiar, or so I thought — unmistakable, really.

To this day, in the field, I have some difficulty separating the songs of the two forms (which may be separate species soon, for those of you just tuning in).  Both are remarkable vocalists, with long-running musical strings of jumbled high-pitched notes and trills:

Winter Wren song, Hampshire County, Massachusetts, 20 June 2008. Recording by Andrew Spencer.
Winter Wren song, Hampshire County, Massachusetts, 20 June 2008. Recording by Andrew Spencer.
Pacific Wren song, Humboldt County, California, 28 March 2009.
Pacific Wren song, Humboldt County, California, 28 March 2009.

It’s not as easy as separating them by call, but with practice, Winter and Pacific Wrens are usually distinguishable by song.  Here are some points to consider:

  • First of all, in the above examples, don’t let the shorter Pacific song fool you.  Strophe length is variable in both forms, and Pacific’s songs may actually average longer than Winter’s.  Pay no attention to duration!
  • Although I can’t vouch for this across the board, the sample I’ve studied strongly suggests that Pacific Wren tends to sing with more trills given closer together, so that the song is composed of >50% trills, while Winter Wren tends to sing with longer jumbles of individual notes and fewer trills more widely spaced, so that the total song consists of <50% trills.
  • Tone quality is key. Many people consider the song of Pacific to be “drier,” or, in the words of Sibley, “more mechanical-sounding” and “buzzy” with “hard trills.”  The difference is one of musicality.  To my ear Pacific’s song sounds higher-pitched, but you’ll note on the spectrograms that the maximum and minimum frequencies of both songs are almost exactly the same.  The difference is that Winter Wren shows very little frequency change within individual notes (with the trills usually clustered at the bottom of the song), while almost every one of Pacific Wren’s individual notes sweeps from below 4 kHz to about 8.  Thus the difference is roughly equivalent to the difference we saw between the songs of Field Sparrow and Black-chinned Sparrow.  The Pacific Wren’s notes, especially its trills, are less musical because they are changing pitch too rapidly.  Practically every single one of the Winter Wren’s notes has a bell-like, musical quality, but the Pacific Wren has a much lower percentage of musical notes.

A good way to think of the difference in tone quality is to listen for the trills inside the wren songs and compare them in your head to the the “classic” song of Dark-eyed Junco and the “classic” song of Chipping Sparrow (which are, of course, themselves often difficult to separate by ear).  The Winter Wren tends to have the more musical, junco-like trills, while the Pacific Wren often trends towards an unmusical, Chipping Sparrow-like (or even Brewer’s Sparrow-like) lisping rattle.

Song delivery also differs, although this can be difficult to ascertain unless you have a great auditory memory.  Winter Wren males have only a few stereotyped songs in their repertoire; successive strophes of song are almost always identical.  Pacific Wren males sing with far more songtypes, and they also recombine their songs — the beginning notes of successive strophes are frequently identical, but the endings vary widely.

For more practice, and to hear some more of these fantastic bird songs, head over to Xeno Canto’s Winter/Pacific Wren collection.

Pacific Wren, Part One

Pacific Wren, Part One

Pacific Wren, Seattle, Washington. Photo by Tom Talbott (Creative Commons license 2.0).
Pacific Wren, Seattle, Washington. Photo by Tom Talbott (Creative Commons license 2.0).

The American Ornithologists’ Union Checklist Committee recently updated its slate of taxonomic proposals.  Lots of exciting stuff here, including proposed species status for our old friend, the South Hills Crossbill, and a split of Western Scrub-Jay.  The proposed split I want to focus on today, though, is one that’s long in coming, and quite likely to pass, in my opinion: the split of Winter Wren into eastern and western North American species.

Why split the Winter Wren?  For starters, eastern and western populations are 8.8% divergent in their mitochondrial DNA.  (Trust me, that’s a lot.)  Songs and calls differ diagnosably.  Furthermore, the two forms nest side-by-side in the northern Canadian Rockies without interbreeding.  Analysis of vocalizations and genetics haven’t turned up anything that really looks like a hybrid.  Really, this looks like a pretty straightforward split, even by the “old” biological species criteria.

So, it looks like come next summer, we’ll probably have a new taxonomy in the genus:

  • Winter Wren, Troglodytes troglodytes: breeding from east-central British Columbia east across Canada and down through the Appalachians; wintering in the eastern United States, mostly east of the Great Plains.  It’s highly likely that this species will eventually be split from the Eurasian birds, in which case the scientific name of our Winter Wren would revert to Troglodytes hiemalis, a direct translation of its common name in America (Eurasian birds are usually just called “Wren”).
  • Pacific Wren, Troglodytes pacificus: breeding in Alaska through the northern Rockies to the Yellowstone area and down the Pacific coastline to Central California; mostly non-migratory, though wandering casually southward in winter.  The distinctive Aleutian birds would be included in this species.

How do you tell the two apart by sound?  For today, we’ll look at the calls, which is the easiest way to identify them, especially in winter.

Calls

Winter Wren calls, Phillips County, Arkansas, 30 March 2006.
Winter Wren calls, Phillips County, Arkansas, 30 March 2006.
Pacific Wren calls, Humboldt County, California, 28 March 2009.
Pacific Wren calls, Humboldt County, California, 28 March 2009.

With direct comparison of soundtracks and spectrograms, the differences are obvious.  The Winter Wren’s call is much clearer, with discrete harmonic bands; both spectrographically and aurally it is reminiscent of the call of Song Sparrow.  The Pacific Wren, by contrast, has a call that is much noisier and higher-pitched, and, on average, slightly briefer.  It is often compared to the call of Wilson’s Warbler.  Although the call may not look higher-pitched on the spectrogram (since the minimum and maximum frequencies of both calls are about the same), note that the darkest part of the Pacific Wren spectrogram (and therefore the loudest part of the call) tends to concentrate around 6-7 kHz, while the darkest part of the Winter Wren spectrogram comes in at about half that.  This accounts for the perceptual difference in pitch.

In my next post I’ll look at how to tell these two species apart by song.  As these two are both fantastic singers, it will be a melodious post indeed!

Let’s Get Exotic

Let’s Get Exotic

Here’s another quiz sound from Boise.  Can you identify it?

Isn’t that the world’s most fantastic sound?  And talk about distinctive.  The panelists asked me if it was even a bird.  🙂  Yes, it’s a bird, and I recorded it in Orange County, California, in March 2009.  Here are a couple more wonderful noises from the same species:

The bird is Red-crowned Parrot (Amazona viridigenalis), and as I quickly discovered when I arrived at Santiago Oaks Regional Park for a morning of recording, its bizarre and stentorian voice has become one of the characteristic sounds of suburban Orange County.  On the freeway that morning I had seen large flocks of parrots coming off of night roosts, but I wasn’t able to identify them.  In fact, I didn’t know which species of parrot I was dealing with at Santiago Oaks until well after I got home.  My first tentative identification in the field was Lilac-crowned Parrot (Amazona finschi).  Red-crowneds and Lilac-crowneds look surprisingly alike, and I didn’t have a way to compare their calls.

Why not? Because like other exotic species, parrots are woefully underrepresented in commercial bird sound publications.  Bird Songs of California by Geoff Keller doesn’t include any parrots.  The Stokes Field Guide to Bird Songs (Western Region) has the Red-crowned, by dint of its establishment in South Texas, but it doesn’t have the Lilac-crowned.   Nor any of the other thirteen parrot species that have “established naturalized populations” in California per the California Parrot Project.

Partly, of course, exotic birds are underrepresented in sound collections because they have traditionally been underrepresented in field guides and checklists.  Before making a species “official,” state records committees and the AOU and ABA checklist committees want to be certain the birds have established enough of a population to ensure their long-term survival in their adopted land.  And that’s valuable information.

In the meantime, however, whether their immigration status is legal or not, the exotic birds are unquestionably here, and they are unquestionably making noise.  And that presents us with a great opportunity — first, to learn the voices of the newest members of our local avian soundscape — and second, to get recordings, sometimes right in our own backyard, of species that might be rare, little-known, and hard to encounter in their native range.

But wait.  Are the recordings of exotic birds “legitimate”?  “Authentic”?  Are they going to sound the same as they do where they came from?

Well, that depends.  If the species is one with an innate song, then the answer is almost certainly yes.  The millions of Eurasian Collared-Doves in this country sound very much like the millions in Europe and Asia, because collared-doves don’t learn their songs; they inherit them genetically.  Some birds do learn their songs, however, and those songs may well change, especially over time, if the soundscape changes around them.  Most birds with learned songs are apparently genetically predisposed to pick out the sounds of their own species from the chorus and imitate those, but if they’re first- or second-generation immigrants in an avian Babel, they might not have many, or any, of their own species to learn from.  Might the scarcity of conspecific tutors restrict the repertoire size of immigrants?  Might it force them to innovate or imitate other species?

We don’t really know.  And that’s one of the main reasons why exotics are worth recording.  We could learn a lot about the cultural transmission of song by recording, say, Red-whiskered Bulbuls in Florida or California.  We could learn a lot about the biological components of song by recording hybrid birds, which may be more frequent among exotics.  We could learn a lot about what these birds sound like in their native ranges without having to travel there ourselves.  Even the “lowly” House Sparrow might have a lot to teach us, if we set out to discover whether regional dialects have begun to appear in North America since the species first landed here in 1852.

So it’s time for another call to action from me.  Record exotic birds.  Record starlings, collared-doves, House Sparrows, House Finches, Ring-necked Pheasants, Common Mynas,  partridges, parrots, and pigeons, because they’re slipping under the radar and they have a lot to teach us.  In common parlance, “exotic” is the opposite of “boring,” and I think that’s the way it should be with birds as well.

The Crossbill Quiz: Answers

The Crossbill Quiz: Answers

Here are the answers to the quiz from the last post:

a. Type 4

Type 4 is believed to specialize on the cones of Douglas-fir.   It is widespread but somewhat irregular in its distribution: it is usually common in moist forests of the Pacific Northwest and can be frequently found in dry forests there also.  It is regular in southeast Arizona, and indeed this particular recording was made at Barfoot Junction in the Chiricahuas in May 2009.  It appear to be absent some years from Colorado, but fairly common in other years; 2009 saw a decent influx of this type into the state.

Ken Irwin (unpubl.) has proposed that hidden inside Type 4 there is another call type,  Type 10, that specializes on sitka spruce in coastal California.  It’s still unclear to me whether Type 10 is a separate call type or just a variation on Type 4.  Whatever the case, Type 10 seems to wander widely, at least across the northern states, out to New England and Maryland.

The Type 4/10 group, as a whole, sounds very distinctive because of its upslurred calls.  It may be a little hard to hear that they are upslurred because they are delivered so fast, but the rising, flicking quality of the calls is pretty distinctive, reminding some people of the “whit” calls of Empidonax flycatchers.

b. Type 9, the South Hills Crossbill

This type is sedentary and restricted to the South Hills and Albion Mountains of Idaho, where it feeds on the local variety of lodgepole pine.  It sounds kind of like Type 2, clear, simple, and downslurred, but it is noticeably low-pitched.  I think it is kind of “dull-sounding,” without much ring or resonance, but I’d be interested to hear how other people describe the difference.  I recorded this in the South Hills in September 2009.

c. Type 2

Here’s a Type 2.  This is probably the most numerous crossbill in North America; it is common almost everywhere Red Crossbills can be found.  It is surmised to specialize on ponderosa pines.  Across its range its calls are variable, but the high-pitched, clear, downslurred quality is fairly distinctive.  This recording was made in Boulder County, Colorado, in July 2007.

d. Type 3

This is one of the smallest crossbills (only Irwin’s proposed Type 10 is similarly small) and is one of the most common crossbill types in moist northwestern forests, apparently specializing on western hemlock.  It also can be found across the boreal forest, occasionally into New England, and it wanders rarely into the southern Rockies — there are now two certain records for Colorado and more in the “probable” category.  There are also recordings from Arizona.

Types 3 and 5 sound similar to my ear: they are more complex than the types we heard above, less clear and less obviously upslurred or downslurred.  Type 3 is the duller-sounding of the two, but I must admit I need practice with this identification.  This particular recording, the second-ever for Colorado (from the Grand Mesa, February 2009), was made by Andrew Spencer when I was right beside him–and I didn’t turn on my microphone because I thought they were “just” Type 5s.  To be fair, Andrew recorded them because he thought they were White-winged Crossbills.  🙂  He didn’t identify them until days later when he looked at the spectrogram.

e. Type 5

This is the “other” common crossbill in Colorado (besides Type 2), a widespread bird of high elevations in the West, apparently adapted to feed on lodgepole pine but also very fond of Engelmann spruce.  In direct comparison I think it sounds more “metallic” than Type 3, but it’s a tough call in the field.  A distant flock can sound a lot like a bunch of crickets.  This recording was made in Larimer County, Colorado, in June 2009.

The Crossbill Quiz

The Crossbill Quiz

Last week I facilitated the Sound Identification Panel at the Western Field Ornithologists Conference, which is a wonderful privilege I have been treated to for each of the last four years.  For those who don’t know, the Sound ID Panel is an annual WFO tradition started by Sylvia Gallagher. In front of a large live audience, a moderator (that’s me) quizzes an expert panel on the identification of mystery bird sounds.  This year our panelists were Ted Floyd, Oscar Johnson, Jon Feenstra, Rich Hoyer, and Tayler Brooks, and I must say they did an outstanding job.  In collaboration with each other, and notwithstanding the occasional wrong answer, they managed to identify almost every mystery sound in the end, and believe me, that’s not an easy feat.

In 2009 I decided to cross a line I’ve been reluctant to cross in the past.  I put Red Crossbills in the mix.  It seemed natural, since the conference was in Idaho, home to the endemic South Hills Crossbill, and our keynote speaker was crossbill guru Craig Benkman.  I gave the panel the following quiz:

Red Crossbill Call Types: Matching

In this quiz you’ll hear one example of each of the four most common and widespread crossbill types in the western United States, listed below with the tree species they are believed to specialize on:

  • Type 2 (Ponderosa Pine)
  • Type 3 (Western Hemlock)
  • Type 4 (Douglas-Fir)
  • Type 5 (Lodgepole Pine, Rocky Mountain variety)

Plus, given the location of the conference, we’re tossing in the sedentary and range-restricted South Hills Crossbill, endemic to Idaho, which has been proposed as a separate species, Loxia sinesciuris:

  • Type 9 (Lodgepole Pine, South Hills variety)

Here are the sound clips in random order.

a.

b.

c.

d.

e.

How well can you do?  Answers will be posted in a subsequent message.

The Coolest Bird Sound

The Coolest Bird Sound

In the opinion of the late Rich Levad, the Black Swift was The Coolest Bird, and in his still-unpublished manuscript of that name, he advanced a pretty strong argument for its coolness.  This is a bird that spends much of its time foraging so high in the air that nobody ever sees it.  It nests in the spray zone of waterfalls, so that a juvenile may never have dry feathers between hatching and fledging.  And it is poorly understood: to this day we really have nothing but educated guesses as to where the species spends the winter.

It appears that will change soon. My friend Jason Beason of Rocky Mountain Bird Observatory sent me this announcement:

As of the evening of August 24th there are three Black Swifts in Colorado wearing light-level geolocators! On that evening, Kim Potter, Carolyn Gunn, Todd Patrick, Chuck Reichert, and myself caught ten adult Black Swifts using mist-nets in the Flat Top Mountains in western Colorado. The locators were placed on two females and one male, all of which weighed greater than 50 grams (the minimum cutoff to stay less than 2% of total body weight). In just a few weeks the swifts will begin their migration to locations unknown. With string and ribbon included the total weight we added to the birds was only 1.8 grams! With luck, this time next year we will be able to report where these birds spent the winter of 2009-2010. If not for the help of Carolyn Gunn, a trained veterinarian with very nimble hands, we could not have placed these devices on the swifts in a reasonable amount of time. We are very thankful that she agreed to help with this project!

Black Swift in hand with geolocator. Photo by Carolyn Gunn.
Black Swift in hand with geolocator. Photo by Carolyn Gunn.

The light-level geolocators that Jason referred to are the same technology used by Stutchbury et al. 2009 to estimate the migratory paths of Wood Thrushes and Purple Martins, birds too small to carry the satellite transmitters like those the Pacific Shorebird Migration Program has placed on Bristle-thighed Curlews and Bar-tailed Godwits in recent years.  Jason later reported to me in a follow-up email that a fourth Black Swift was outfitted with a geolocator at Box Canyon, near Ouray, on 29 August.  Unlike the satellite transmitters, the geolocators do not send data in realtime; it will be lost unless the birds are recaptured next year and the data downloaded.  Since Black Swifts are extremely faithful to their nesting sites, the team thinks there is a good chance they will be able to retrieve one or more of their geolocators a year from now.

One of the reasons Black Swifts are so little known is that they are rarely observed, even near their nest sites.  I believe that one of the reasons they are rarely observed is that most people don’t know what they sound like.  Unfortunately, one of the reasons why most people don’t know what they sound like is that they’re devilishly difficult to record.  Over the past couple of years I’ve found that Black Swifts are actually quite vocal, particularly near the nest — but the nests are usually so near waterfalls that recording is basically impossible.

Thanks to Rich Levad and his army of Black Swift volunteers, the number of known nesting sites in Colorado has more than tripled in the last decade, and at some of these sites, it’s possible to get a reasonable recording.  With better recordings comes a greater chance of detecting Black Swifts when they are overhead.  I have sometimes been able to find this species by ear when I wasn’t expecting it or looking for it, and I’m not the only one.  So let’s spend some time on identification by ear.

The individual “pip” notes of the Black Swift are extremely similar to the “pips” of Pygmy Nuthatches, and they can sound similar to some notes of Red Crossbill.  Rarely, the swifts will make a longer, higher-pitched “squeak” noise.

Black Swift vocalizations, Larimer County, CO, 23 August 2007.
Black Swift pip & squeak calls, Larimer County, CO, 23 August 2007.

Sometimes Black Swifts give a relatively stereotyped “extended call” that starts with a rapid twittering series of “pips” and culminates in a clear “squeak.”  This is often followed by a decelerating series of “pips.”

Black Swift extended call, Larimer County, CO, 23 August 2007.
Black Swift extended call, Larimer County, CO, 23 August 2007.

Black Swift vocalizations in general, and the extended call in particular, appear to be correlated with aerial chases, although all vocalizations are also given by some solo flying swifts and by perched individuals at or near the nest.  Nor are these vocalizations limited to the daytime: at least at their nesting sites, Black Swifts will vocalize throughout the night.

You can hear more examples of Black Swift recordings in Xeno-Canto’s collection.

Mountain Quail after all?

Mountain Quail after all?

Don Roberson of Creagrus fame sent me an interesting and provocative email in response to the old pygmy-owl vs. chipmunk thread (1 2).  With his permission, I’m reproducing it here for discussion:

A possible word of caution regarding analysis of chipmunk calls as discussed at http://earbirding.com/blog/archives/454:

I don’t necessarily disagree with your conclusions, but there are caveats to be considered. You may have already considered them, but on the off chance you have not, here they are.

1. You rely heavily on Brand (1976) for your starting point, and he studied primarily “Townsend’s Chipmunk” as stated. However, this was prior to the acceptance of the split of “Townsend’s” into four species, as proposed by Sutton & Nadler (1974) and Sutton (1987) [citations below]. Now, the 4-way split is universally accepted.

One of the major reasons for the split was the differences in vocalization between the four species. One of the two papers, probably the 1987 one, goes heavily into differences in calls. It has been a while since I’ve read them, and I don’t recall whether he went into “chips” versus “chuks” but a full background in the vocal differences between the for “Townsend’s” types is important before drawing generalizations from Brand’s 1976 paper. I don’t know how many species of chipmunk Brand reviewed, but there are 25 species in North America.

For more on chipmunk i.d., with some discussion of calls, see my 3-page web set on chipmunk i.d. that starts at
http://creagrus.home.montereybay.com/chipmunks.html
The Townsend’s four-way split and i.d./calls is on page 2 of the set;

2. The call you have posted as probable Merriam’s Chipmunk “chuk” is a very commonly heard vocalization at Chews Ridge. I live in Monterey County and probably know the spot better than any other birder. I have never seen a chipmunk giving the call, although Merriam’s is common there. In fact I have puzzled over what does give the call. I have cautioned many times about claims of pygmy-owl there because of this note. However, I have generally attributed the note to Mt. Quail. In doing Breeding Bird Atlasing there and other similar habitats in the Santa Lucia Mts., there have been circumstances when a Mt. Quail was seen not long after and close to the source of the call.

If it is Merriam’s Chipmunk, that is very interesting, because it can be given in a steady and prolonged series that I haven’t attributed to chipmunks. [On the other hand, ground-squirrels do give a series of steady, prolonged, evenly-paced calls, so it is reasonable that a chipmunk would as well.]

Did any of your correspondents actually see a chipmunk doing these series of steady calls in California? I do think this could be the right answer to the mystery, but I would appreciate some analysis on why it is not a Mt. Quail.

Thanks, Don

Sutton, D. A. 1987. Analysis of Pacific coast Townsend’s Chipmunks (Rodentia: Sciuridae). Southwestern Naturalist 32: 371-376.

Sutton, D. A., and C. F. Nadler. 1974. Systematic revision of three Townsend’s Chipmunks (Eutamias townsendii). Southwestern Naturalist 19: 199-211.

In response to a couple of Don’s questions, I’ll say:

  1. Chipmunks definitely do give long steady series of call notes, both “chips” and “chucks”; the probable Least Chipmunk I recorded in Michigan vocalized at a nearly constant rate for over 12 minutes.  I did visually identify that one as a chipmunk, although didn’t make a visual ID to species.
  2. Some of my correspondents have seen chipmunks making pygmy-owl-like sounds in California, although it’s apparently more common for the source of the sound to be unseen.
  3. I have tracked down the two sources Don cited; if you want PDF copies, email me.  The 1987 paper mentions vocal distinctions only briefly, citing a personal communication from William Gannon and publishing no spectrograms.  Another paper may go into the differences; I haven’t found it yet, but I haven’t searched long either.  Gannon gave a paper at one point — Influence of proximity to rivers on chipmunk vocalization patterns. Gannon, William L. Special Publication the Museum of Southwestern Biology. 1997 24 March; 3:273-285 — but I haven’t had a chance to track it down yet.

I think we may have a lot to learn about chipmunk vocalizations!  Comments?

Another Chipmunk Mystery

Another Chipmunk Mystery

This past week I was in Michigan, where I had an opportunity to get out and do some recording on a couple of mornings.  My earlier posts (1 2) on chipmunk “chuck” calls had stimulated my curiosity in mammal sounds, so when the chipmunks started calling all around me, I turned on the mic — and lo and behold, I got something pretty interesting:

Chipmunk "chuck" call, Peshekee Grade Road, Marquette Co., Michigan, 8/6/2009 (20-43).
Chipmunk "chuck" call, Peshekee Grade Road, Marquette Co., Michigan, 8/6/2009 (20-43).

I was struck by the similarity of this sound to the mystery call from California that was probably made by a Merriam’s Chipmunk.  I can confirm that the Michigan sound came from a chipmunk: after a few minutes of hunting I spotted the little guy on the ground only 10 feet away, twitching his head forward slightly with each call.  Unfortunately, I was under the mistaken impression at the time that only one chipmunk species inhabits the Upper Peninsula of Michigan.  Upon returning home, I discovered that the U.P. actually has two species, Least and Eastern:

Least Chipmunk photoEastern Chipmunk photo
Least Chipmunk (Tamias minimus), Glacier National Park, Montana. Photo by Phil Armitage. Eastern Chipmunk (Tamias striatus), Bas-Saint-Laurent, Quebec. Photo by Gilles Gonthier (Creative Commons 2.0).

If I had been paying attention, I could have identified the little guy to species by looking at his size, shape, and facial striping — but I wasn’t paying attention, so now, alas, I have to use the recording to figure out which ‘munk was chipping.

And there’s the rub.  The vocalizations of Least and Eastern Chipmunks have been described in the literature (e.g., Bergstrom & Hoffman 1991, Burke da Silva et al. 1994), but I can’t find a published spectrogram of this particular sound.  Nonetheless, the evidence points to this being the “chuck” call of Least Chipmunk.  Reasons:

  1. The “chuck” call of Eastern Chipmunk has been well studied, and I’ve heard a couple of recordings of it (e.g., this one), which sound nothing like what I recorded;
  2. The Michigan sound is similar to the probable Merriam’s Chipmunk “chuck” from California, and all western chipmunk species (including Least) are supposed to have similar “chucks,” according to Brand (1976).  Eastern Chipmunk is not closely related to other North American chipmunks.

The Least Chipmunk is the most widespread chipmunk species in North America, occurring throughout much of the Rocky Mountain and Great Basin regions, plus the boreal forest from the Yukon to the U.P. and southwest Quebec. In much of its range it is common, and in many places it is the only chipmunk.  So, those of you who know something about chipmunk vocalizations, this one’s for you: has anyone heard a sound like this from a Least Chipmunk?  How about from an Eastern?  How good is my tentative ID?

Gray Hawk, continued

Gray Hawk, continued

In my last post, I discussed differences in the alarm calls of Gray Hawk (for the purposes of this post, Buteo plagiatus) and Gray-lined Hawk (here, Buteo nitidus — see the last post for taxonomic rationale).  Over the past few days, I have gone through the Gray Hawk sound collection at the Macaulay Library, which has given me some new information.

In my last post I said the alarm calls of Gray and Gray-lined Hawks tend to be “fairly stereotyped within populations.”  In light of what I’ve learned from the larger sample size, I think it’s worth retracting that statement in favor of something like, “the alarm calls of Gray and Gray-lined Hawks are variable within populations, and even within individuals, but are nonetheless consistently separable on several characters.”

Of the characters I mentioned in my last post, the most consistent seems to be energy spectrum; those differences seem consistent across the entire sample size.  Differences in frequency and pattern of inflection are also pretty reliable, although there are anomalous birds here and there.  The differences in duration are tricky, though, since several Gray-lined Hawk vocalizations from Venezuela clock in at around 1.75 sec in length.  It’s clear there is a lot of overlap in this character.

Here are some other ways in which the alarm calls vary:

  1. The noise content of alarm calls in both Gray and Gray-lined Hawk is highly variable.  A clear tone quality (that is, without noise) is the norm in both taxa, but noisy calls are not infrequent, and some birds in both taxa may give noisy and clear calls on the same recording.
  2. Within the context of the constant differences in energy spectrum, phase shifts (period doubling, period tripling, etc.) are common in both taxa, as they seem to be in many species of raptors.

I hope to publish more on Gray Hawks (and other bird sounds) soon, but as I’m in the middle of an unplanned trip, I may not get to it until next week.  Sorry!