Identification – Page 6

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

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

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

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

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

Here are some things I liked less about the site:

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

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

Evening Grosbeak Call Types

21 March 2010 Nathan Pieplow

Evening Grosbeak, Soda Springs, CA, 8/3/2009. Photo by C.V. Vick (Creative Commons 2.0).

In 2004, a paper appeared in the Condor by Kendra Sewall, Rodd Kelsey and Tom Hahn that described several different variants of flight calls in the Evening Grosbeak. Their fascinating research immediately reminded many of the work on the call types of Red Crossbill, and I heard a few people worry out loud about whether a split of Evening Grosbeak might be in the works.

But there’s no cause for worry. The “call types” of Evening Grosbeak are not as scary as the call types of Red Crossbill. While Red Crossbills sort into at least 10 call types in North America, Evening Grosbeaks apparently sort into just 5. And while multiple Red Crossbill call types often occur in one area (which is part of the justification for splitting them into separate species), the Evening Grosbeak call types usually stay in fairly well-defined, separate geographic ranges. In fact, Sewall et al. note that the five call type groups seem to match the five subspecies groups in a decades-old taxonomy.

Learning to identify Evening Grosbeak call types is a fascinating exercise, especially if you come upon a wandering flock and want to know where they likely originated. This post aims to provide an introduction to the different “types” and how to tell them apart.

“Flight calls” vs. “Trills”

The terminology used by Sewall et al. (2004) as well as the BNA account of Evening Grosbeak distinguishes two main calls that are typically heard from the species: “flight calls” and “trills.” Neither source mentions how the “trills” may vary among groups; this post is going to concern itself solely with the flight calls, which are the most common vocalizations.

Type 1

Range: The northern Rockies and the Cascades, from at least British Columbia south to Oregon, northern Wyoming, and the Black Hills of South Dakota. Wanders to the northern Sierra Nevada and to Colorado.

Flight call:

Even though the spectrogram shows that it tends to start at a higher frequency than other types, Type 1 sounds relatively low-pitched, especially compared to Types 2 and 4. It has a very clear sound that is distinctive once you learn it. More than the other types, this one reminds me of a particular Pine Siskin call (but beware! Pine Siskins can mimic other Evening Grosbeak types in their songs). Here’s another good recording of Type 1.

Type 2

Range: The Sierra Nevada of California; wanders at least occasionally north to southern Washington.

Flight call:

To my ear, this sounds like the clearest, most purely whistled type, even clearer than Type 1, but it is distinctly higher-pitched and more piercing than Type 1. Type 2 is quite similar to Type 4 and the two may be difficult to distinguish by ear in the field (see below).

Type 3

Range: Boreal forests of Canada east of the Rockies and in the northeastern United States. Wanders south throughout the East.

Flight call:

The distinctive Type 3 differs from Types 1, 2, and 4 by being slightly longer and lower-pitched and distinctly burry. Field guides with an eastern focus have often compared the calls of Evening Grosbeak to certain vocalizations of House Sparrow, and Type 3 is the reason why.

Type 4

Range: The southern Rockies (Colorado and New Mexico), occasionally wandering north at least to the vicinity of Jackson Hole, Wyoming.

Flight call:

The high-pitched and piercing Type 4 flight calls are most similar to Type 2 flight calls, both on the spectrogram and to the ear, but slighty huskier and less clear. I’m not certain I could tell them apart in the field with confidence, but the two have never yet been recorded in each others’ range to my knowledge. Here’s another recording of Type 4.

Type 5

Range: The Sierra Madre of Mexico, north to southeastern Arizona.

Flight call: To my knowledge, only one recording of this type has been made, and here it is:

Evening Grosbeak Type 5 flight call, Arizona. Recording by Rich Hoyer (used here with permission). — Evening Grosbeak Type 5 flight call, Cochise County, AZ, 4/14/1999. Recording by Rich Hoyer (used here with permission).

If this recording is typical, then Type 5 is distinctive: even longer and burrier than Type 3, but high-pitched like Types 2 and 4. If I had to guess, I’d say that the doubled rhythm is probably due to the whim of this individual bird, not characteristic of Type 5 in general, but who knows? — maybe Type 5 is the Mountain Pygmy-Owl of Evening Grosbeaks. If you have any recordings of Evening Grosbeak from Arizona or Mexico (or you know someone who does), please let me know!

Regions of Mystery

There are some places where we don’t really know which type to expect:

Southwest Oregon and northern California: Types 1 and 2 have both been recorded in this region, and the actual limits of their distribution here are poorly known.
Black Hills of South Dakota: The one recording I have is of Type 1, but I think Type 3 might also be likely, and Type 4 might wander in.
Arizona: My guess would be that Type 4 is most common in the northern and central parts of the state, while Type 5 is the most likely type to be encountered in the southeastern mountains, but we need more data.

You know what that means: more recordings necessary!

The Mysterious American Tree Sparrow

14 January 2010 Nathan Pieplow

American Tree Sparrow, 2/11/2007. Photo by Eric Begin (Creative Commons 2.0).

A frequent topic of discussion on this blog is what we don’t know about bird sounds. Another favorite topic is how amateur recordists might help solve mysteries — and advance science — by recording common birds in their own backyards. Now, as most of North America languishes in the middle of a deep, dark winter, I’d like to point out a golden opportunity for citizen science — a chance to answer questions about a bird that many people know, but few really understand.

I never used to pay much attention to American Tree Sparrows. In the places I lived, they weren’t common enough to be really familiar, but they weren’t rare enough to be noteworthy either. For the first couple of years that I recorded bird sounds, I made no particular effort to record them, even though they can be found in winter with ease not far from my house. I just didn’t think they had much to say.

Boy, was I was wrong.

In fact, American Tree Sparrows appear to have one of the most varied vocal repertoires of any sparrow. I’ve recorded winter flocks on about a dozen occasions now, and listened to a good number of recordings at the Macaulay Library. The more I listen, the more mystified I become.

The most distinctive winter vocalization of the American Tree Sparrow is the “flock call,” described by many authors as a two- or three-syllabled musical note:

American Tree Sparrow flock calls, Yuma County, CO, 12/27/2008.

In and of itself, I find the flock calls interesting, because they sound so different from anything I hear from other sparrows, and because the spectrogram shows them to be so complex. But the more recordings of flock calls I made, the more confused I got, because it started to look like no two flocks give the same flock calls:

American Tree Sparrow flock calls, Lincoln County, SD, 12/13/2009.

American Tree Sparrow flock calls, Brown County, SD, 12/15/2009.

The incredible variety between individuals (and within individuals) strongly suggests that the flock calls of American Tree Sparrows are learned, not innate. This is interesting and unexpected; as far as I know, complex learned calls are unknown in any of the Tree Sparrow’s close relatives.

Even more interesting is that the limited sample of recordings I’ve studied seems to hint that flockmates give flock calls that are, if not identical, at least broadly similar — while a flock just down the road might sound different. Will further recordings support this observation or disprove it? Either result would raise further questions. Do Tree Sparrows learn their flock calls on the breeding grounds, during migration, or on the wintering grounds? Do they change their flock calls over time? If they learn from flockmates, are flock calls a way of keeping the same group of birds together all winter? If so, why? What happens when a bird with a different kind of call joins a flock?

At first glance, the situation surrounding these complex, apparently learned calls bears more resemblance to the vocal repertoires of some cardueline finches than to the vocal repertoires of any other North American sparrow. Unraveling the entire mystery would be a good dissertation topic for some motivated doctoral student in ornithology.

But I’m short on motivated doctoral students at the moment. Here’s my question: can amateur recordists get a start on solving these questions? I’d like to find out.

If you’ve got recording equipment and ready access to American Tree Sparrows, I challenge you to get out and make some recordings of your local flock.

Take notes out loud while you are recording (not the entire time, of course; it’s necessary to let the birds speak uninterrupted for at least part of the recording). In your notes, mention the date, the location, the weather, and the species — and most importantly, try to say what you observed the birds doing, and which sounds correlated with which behaviors, and which individuals were vocalizing when.
If you’ve got a local flock that sticks around most of the winter, follow it over time and pay attention to how many birds it includes. Do flocks split and re-merge? Do they stay separate over the course of the winter? If the number of sparrows in your hedge varies from 5 to 50 and back all winter, we can surmise that flocks split and merge.
Let me know of what you are doing via email. If people actually do this and we collect enough data, we might be able to answer some of the basic questions about these flock calls, and we might be able to put together a paper for publication.

Anybody out there up to the challenge?

How I Listen

11 December 2009 Nathan Pieplow

David Sibley was gracious enough to reply to my recent post on Buff-collared Nightjar, first in a comment on my blog, then yesterday in a post on his own blog. He takes issue with me on at least one point:

Nathan Pieplow seems to suggest that, for decades, observers have misidentified Vermilion Flycatchers as Cassin’s Kingbirds, and then mistakenly written that Cassin’s Kingbird sounds like Buff-collared Nightjar.

I guess I did seem to suggest that, but I didn’t really intend to. Instead, I think I meant, “an authoritative source once misidentified a Vermilion Flycatcher as a Cassin’s Kingbird, and for decades, authors have perpetuated the error by simply citing the published assertion that Cassin’s Kingbird sounds like Buff-collared Nightjar.” Given what David wrote in his comment and his post, even the latter assertion by me is a little unfair to him at least, and perhaps to many of the other people I mentioned in that post, since David didn’t just blindly repeat the conventional wisdom; he had field experience to back it up. (However, see his post for an interesting discussion of how the conventional wisdom might have influenced his field experience.)

Overall, though, regardless of who (mis)identified what, David has started a very interesting and, I think, important discussion about a sea change that may be occurring in how birders listen to bird sounds. He writes:

I learned bird songs decades ago through countless hours of field experience, supplemented by listening to a few recordings, reading detailed descriptions, and talking to other birders. It was a subjective, holistic approach to bird songs that led to a sort of gestalt style of identification – after you hear a sound often enough the identification just becomes second-nature.

Now, it still takes countless hours, but birders have a wealth of technological aids, allowing them to study and compare bird sounds with an ease and immediacy that was never possible before. In the modern world of ipods, sonagrams, and websites like xeno-canto, birders can examine the bird sounds directly, objectively, and in great detail. This may lead (as Nathan Pieplow admits) to a slightly greater emphasis on differences in pattern rather than the more subjective and hard-to-describe differences in tone.

Given how suggestible we are, and how tiny things can influence our perception, the detail-oriented objective approach to bird sound identification is probably better and more accurate. A similar shift happened in sight identification a couple of decades ago, and that shift can also be linked to technology. In the 1980s it was rapidly improving photographic equipment and optics that allowed more detailed study and comparison of living birds than ever before, leading to a whole new approach to identification based on feather details, molt, etc.

It may be that with modern technology Cassin’s Kingbird is no longer such a source of confusion with Buff-collared Nightjar. If so it has merely been replaced by another species (Vermilion Flycatcher) that is less easily sorted by the modern style.

This gives me a lot to think about. Perhaps the different ways in which we learned our bird sounds might provide insight into how David Sibley and I listen to sounds differently. He learned sounds in the field; I learned them on the floor of my bedroom in South Dakota when I was in high school, playing the Peterson Birding By Ear tapes over and over again. Those tapes (which remain the best resource I’ve ever seen for people who want to learn bird sounds on their own) didn’t take a holistic, all-at-once approach; instead they took an analytic approach, grouping similar sounds together and then pointing out key field marks or “handles” — here a distinctive tone quality, there a distinctive rhythm — to distinguish sounds within the groups.

I’ve used this same basic approach to sound identification ever since: recognize a pattern, then focus on a piece of it. The pattern gets you to the right group; the pieces narrow the identification to species. Tone quality is part of this analysis, but not the most important part.

In fact, in some ways I think I place a pretty low priority on tone quality. For several years now, I have been convinced that tone quality is the slipperiest attribute of sound: the hardest to analyze perceptually, the hardest to describe. And I think tone quality is responsible for most of the disconnect between most descriptions of sounds and the sounds themselves. I de-emphasize it precisely because it is so difficult to categorize. Other attributes of sound are much easier to describe and compare, so those are the ones I focus on.

For the most part, I’m just doing what works for me, but I hope it works for other people as well. I really do believe in the objective, analytic approach. On the whole, I don’t think I can say it any better than I said it at the end of my Birding article:

When we set about describing a bird sound in words, we should avoid the temptation to describe how the sound makes us feel or what it reminds us of, since those things exist in us, not in the sound. Instead we should strive to describe what is there: what can be measured with a stopwatch, pointed out on a sonogram, and defined in an empirical fashion. I cannot claim yet to have accomplished this with pinpoint accuracy. But I firmly believe that it can be done, and I firmly believe we should start to do it.

You Misidentified It Wrong

1 December 2009 Nathan Pieplow

For better or worse, this sign usually means "good birding ahead." Cochise County, AZ. Photo by Tom Peck (Creative Commons 2.0).

The Buff-collared Nightjar is a little-known but highly-sought bird from Mexico that can be found in some of the remote canyons of southernmost Arizona. Seeking this nocturnal rarity can feel like a real adventure. On your way to look for it, you’re guaranteed to pass a sign warning you of terrible dangers, intended to dissuade you from wandering around in the lawless border country lest you meet humanity’s worst elements alone in a dark arroyo.

But the dark arroyos of this remote wilderness are precisely where you must venture if you want to hear the remarkable song of the Buff-collared Nightjar, an evocative rising, bubbly, knocking series that some in Mexico transliterate as préstame tu cuchillo, “lend me your knife” — one of the phrases birders most want to hear from any bird (and, presumably, one of the last phrases they want to hear from a shadowy human figure lurking in the dark thornscrub).

The song of the Buff-collar is so unique that it would seem impossible to mistake for any other bird. But in fact, in the predawn darkness in the very same canyons where the nightjar lives, a strikingly similar sound is often heard from a different bird — a flycatcher that begins its dawn song long before most birders expect day birds to be singing. Over the years, many reports of singing Buff-collared Nightjars have turned out to be flycatchers instead.

According to the classic 1964 publication Birds of Arizona by Phillips, Marshall, & Monson, the source of the nightjar-like dawn song is none other than Cassin’s Kingbird. And this assertion has been repeated by many subsequent credible sources, including Joe Morlan, Kenn Kaufmann (in both North American Birds and in Kingbird Highway), the Arizona Bird Records Committee, the BNA account of Cassin’s Kingbird, and even the Sibley Guide to Birds.

The only problem is, Phillips et al. were mistaken. The dawn song of Cassin’s Kingbird sounds nothing like a Buff-collared Nightjar. It’s the dawn song of Vermilion Flycatcher that causes the confusion. To wit:

Buff-collared Nightjar song, Santa Cruz County, AZ, 5/21/2009. Recording by Andrew Spencer.

(click here for audio)

Vermilion Flycatcher dawn song, Santa Cruz County, AZ, 5/13/2009.

Cassin's Kingbird dawn song, Santa Cruz County, AZ, 6/4/2009. Recording by Andrew Spencer.

(click here for audio)

You can see the resemblance between the first two songs on the spectrogram. Of course there are differences: Vermilion Flycatcher’s dawn song is faster and higher-pitched than Buff-collared Nightjar’s song, with a different tone quality. But the similarity in overall pattern is quite striking.

If you’re having difficulty seeing the similarity between Cassin’s Kingbird dawn song and the first two, that’s because it’s completely different. The spectrogram looks nothing like the others, and the song doesn’t sound anything like the others either. And as far as I can tell, nothing else in Cassin’s repertoire comes any closer to resembling the nightjar. However it happened, it looks to me like Phillips et al. named the wrong bird as the confusion species for Buff-collared Nightjar, and most other authors have followed suit for 45 years.

White-breasted Nuthatch, Part Three

21 November 2009 Nathan Pieplow

During my research for the last couple of blog posts, I’ve arrived at a surprising conclusion: when it comes to regional variation in calls, few common birds are as poorly understood as the White-breasted Nuthatch, particularly the Rocky Mountain and Pacific populations.

In the first two parts of this series we explored the “quank” calls, which are some of the most common vocalizations of the three populations, and the “fast songs.” Today we’ll investigate two more types of rapid-fire calls, the “rapid quanks” and the “hit-trills,” and then I’ll leave the subject of nuthatches alone for a little while!

Rapid Quanks

The term “rapid quank” was coined by Ritchison (1983) to describe the long strings of calls that eastern nuthatches would give in high agitation. The “rapid quanks” are a little tricky to compare among the three populations, because they grade into the regular “quanks,” the “fast songs,” and even the “hit-trills” (see below). In some ways “rapid quank” is just a catch-all term for agitated calls.

In my search through all the recordings available to me, the “rapid quanks” of Pacific birds have been the hardest to find. I suspect this is due to a relatively small sample size rather than a lack of “rapid quanking” by Pacific birds, but I’m not entirely certain of that. (Note, however, some very excited Pacific birds failing to rapid-quank on this recording.)

Above are some relatively rapid short notes from a bird near its nest in California. By comparison, the Rocky Mountain birds sound like they’re on speed:

"Rocky Mountain" White-breasted Nuthatch rapid quanks, San Miguel County, CO, 9/3/2006.

Especially when they get a little bit upset:

"Rocky Mountain" White-breasted Nuthatch rapid quanks, Clark County, NV, 9/27/2007.

As far as I know, nothing but a “Rocky Mountain” White-breasted Nuthatch ever gives notes at this frantic rate (up to 25-30/sec). This type of vocalization is highly variable, however, and I particularly recommend checking out a couple of other distinctive recordings of it, here and here (the latter recording, in particular, is repeated so many times in a row that it could be functioning as a kind of song).

When the “Eastern” nuthatches get excited, they’re still much slower, along the lines of the “Pacific” birds:

"Eastern" White-breasted Nuthatch rapid quanks, Lincoln County, SD, 9/1/2007.

This is about as crazy as they get (in response to an Eastern Screech-Owl tape):

"Eastern" White-breasted Nuthatch rapid quanks, Yuma County, CO, 12/27/2008.

For extra credit, you can listen to more fast-quanking Eastern birds here and here. Note the tendency to revert to paired notes, the “double quanks” of Ritchison (1983), whenever the bird “catches a breath.” Again, beware confusion with the diagnostic disyllabic quanks of Rocky Mountain birds.

Hit-trills

Ritchison (1983) didn’t mention a “hit-trill” vocalization, but he did identify a short contact note he called the “hit,” which is frequently extended into a trill, so I figured the name wasn’t much of a stretch. This is a rather quiet call given in close contact with other nuthatches, and it is very similar in all three populations, although like most of the other calls, it appears to increase in pitch from east to west, and increase in speed in “Rocky Mountain” birds:

"Pacific" White-breasted Nuthatch "hit-trill," Contra Costa County, CA, 3/26/2009. Note begging calls of this species also on the cut (at top of spectrogram).

"Rocky Mountain" White-breasted Nuthatch "hit-trill," Larimer County, CO, 6/3/2007.

"Eastern" White-breasted Nuthatch hit-trill, Monroe County, AR, 3/24/2006. Recording by Randy Little. Macaulay Library #129818.

Click here to listen to the above (at 1:15).

White-breasted Nuthatch, Part Two

16 November 2009 Nathan Pieplow

"Rocky Mountain" White-breasted Nuthatch, Madera Canyon, AZ. — "Rocky Mountain" White-breasted Nuthatch, Madera Canyon, AZ, 4/25/2007. Image courtesy Alan D. Wilson, www.naturespicsonline.com

Last time we looked at the most common calls of the three populations of White-breasted Nuthatch. Here in Colorado, we have both the “Rocky Mountain” and “Eastern” forms of the White-breasted Nuthatch, and I’ve heard a couple of people proclaim that any bird giving a rapid-fire series of calls is a Rocky Mountain individual, while any bird giving a single “yank” note is an Eastern. Unfortunately, it’s more complicated than that. All three populations of the species give rapid series of calls from time to time, so the first thing you’ve got to figure out is which type of call you’re listening to.

Since White-breasted Nuthatches have a lot of different call types, it will probably require several posts to discuss them all. Over the course of this series we’ll mostly follow the terminology of Ritchison (1983) in our discussion of “fast songs,” “slow songs,” “rapid quanks,” and “hit-trills.” Today’s installment looks at the “fast songs.”

Fast songs

Ritchison distinguished between “slow songs” (which we’ll explore in a later post) and “fast songs.” Fast songs consist of rapid strings of simple overslurred nasal notes at a rate of about 10 notes/second, and they appear to be similar in all populations of the White-breasted Nuthatch:

"Pacific" White-breasted Nuthatch fast song, Contra Costa County, CA, 3/26/2009.

"Rocky Mountain" White-breasted Nuthatch, Larimer County, CO, 6/18/2008. — "Rocky Mountain" White-breasted Nuthatch fast song, Larimer County, CO, 6/18/2008.

"Eastern" White-breasted Nuthatch fast song, Tioga County, NY, 3/16/1991. Recording by Steven Pantle. Macaulay Library #53158.

(click here to listen to the above recording at the Macaulay Library)

The length, rate and pitch of fast songs are fairly variable within groups, as far as I can tell, but there appears to be a general trend of increasing pitch as you move from east to west. With more investigation, these differences may turn out to be systematic.

How can you tell when you’re hearing a fast song as opposed to some other vocalization? Two ways:

Rhythm. Fast songs contain long strings of single notes (not double notes like in the “disyllabic quank” call of Rocky Mountain birds) in strict rhythm (not accelerating or decelerating).
Behavioral context. According to BNA, fast songs are given by males hoping to attract a mate; they are often sung loudly many times in a row in late winter and spring. This behavioral context helps differentiate them from some of the “rapid quanks” we will see next, since the two types of vocalizations seem to integrade.

The take-home lesson: long strict series of single nasal notes don’t necessarily identify a bird as a member of the “Rocky Mountain” group. Double notes in series, though, are a good indicator — see the last post for an example.

White-breasted Nuthatch, Part One

10 November 2009 Nathan Pieplow

Eastern White-breasted Nuthatch, 30 September 2008. Photo by Gary Irwin (Creative Commons 2.0). — Eastern White-breasted Nuthatch, 9/30/2007. Photo by Gary Irwin (Creative Commons 2.0).

Birders have known for a number of years now that White-breasted Nuthatches sort out into three distinct vocal groups in North America — Pacific, Rocky Mountain, and Eastern — following a pattern of three-way separation that mirrors those of several other bird species, including the Solitary Vireo complex (split into Cassin’s, Plumbeous, and Blue-headed) and the sapsuckers (split into Red-breasted, Red-naped, and Yellow-bellied).

However, with the exception of field guides, the ornithological literature has been silent on this point. Nobody has done a systematic study on the marked regional variation in vocalizations of the White-breasted Nuthatch. The only in-depth study on vocalizations in the species was done by Gary Ritchison in Minnesota, and so the vocalizations of the Eastern form have been the only ones described in the literature for years; they were the only ones available on commercial bird sound recordings for years too. Even though the Birds of North America account was revised by its authors in 2008, they made no mention of vocal variation, which seems a shocking oversight. Spellman & Klicka (2007) published a molecular phylogeny of the species and found evidence for four distinct clades in the species, with boundaries exactly matching those of the vocal groups (except that they found the Rocky Mountain group was divided into two clades, apparently with identical vocalizations).

Thus, since I can’t find this information anywhere else, starting with this post, I’m going to start exploring these vocal differences in some depth.

“Quank,” etc.

Here are the most common calls of the three nuthatch groups. For simplicity’s sake, we’ll always travel left to right across the country, so you’ll always see Pacific, Rocky Mountain, and Eastern birds in that order.

Pacific White-breasted Nuthach "quank" call, Contra Costa County, CA, 3/26/2009. — Pacific White-breasted Nuthatch "quank" call, Contra Costa County, CA, 3/26/2009.

Rocky Mountain White-breasted Nuthath "disyllabic quank" call, Boulder County, CO, 11/10/2009. — Rocky Mountain White-breasted Nuthatch "disyllabic quank" call, Boulder County, CO, 11/10/2009.

Eastern White-breasted Nuthatch "quank" call, Scott County, MN, 7/6/2009.

The first thing you’ll notice is that the Pacific and Eastern birds sound much more similar to one another than they do to the Rocky Mountain birds. Thus begins a theme we will see repeated many times. Spellman & Klicka found that the Pacific and Eastern birds were sister taxa, separated from one another by the less closely-related birds in the Mountain West. If this seems surprising, remember that the Solitary Vireo complex follows a similar pattern, with Cassin’s and Blue-headed Vireos looking and sounding more like each other than like Plumbeous.

The calls you see above are variable in each of the groups, so some of the differences you see between Pacific and Eastern in call length and overall inflection may not always apply. The most consistent difference seems to be one of pitch: the Pacific birds, with their more widely spaced partials, sound a lot higher-pitched than their huskier-voiced, more nasal Eastern cousins.

Identifying the Rocky Mountain birds, meanwhile, seems like a slam-dunk. Eastern and Pacific birds never make rapid-fire series of call notes, right? Well, actually, yes they do — several different kinds, in fact. I’ll be looking at those in my next post!

A Hybrid Nighthawk?

31 October 2009 Nathan Pieplow

While going through the Macaulay Library’s collection of Common Nighthawk vocalizations, I came upon something strange: a recording of what might be a hybrid Common x Antillean Nighthawk from south Florida.

Here’s some background. In the early sixties, Charles A. Sutherland studied the breeding biology of nighthawks on Key Largo, Florida. He made observations and audio recordings of both taxa breeding there: Chordeiles minor chapmani and the very different-sounding C. m. vicinus, which was not yet recognized as belonging to a separate species (and wouldn’t be until the early eighties, when the AOU would cite vocal differences and sympatric breeding in creating Chordeiles gundlachii, the Antillean Nighthawk).

Common Nighthawk, Rio Arriba County, New Mexico, 6/10/2008. Photo by Jerry Oldenettel (Creative Commons 2.0).

Sutherland wrote up his findings in a 1963 article in Living Bird that remains perhaps the best source published to date on Common Nighthawk vocalizations. Unfortunately, he excluded the Antillean birds from his discussion. On the other hand, he did donate his recordings to Cornell, and now they can be heard online at the Macaulay Library’s website.

Sutherland’s recordings are noteworthy on many levels. For one thing, since he was in the area of sympatry, they often capture the calls of both nighthawk species at once. For another, Sutherland managed to record many rarely-heard vocalizations, such as begging calls of nestling Common Nighthawks, distraction displays by a female Antillean, and the “pik pik pik” notes given by Commons in aerial chases.

In the vocal notes on his recordings, Sutherland often referred to the Antillean Nighthawks as the “pi-ti-mi-dick” birds, after the distinctive rhythm of their calls. There is one individual, however, that he refers to as “the improper pit-i-mi-dick bird,” apparently because the thought its call didn’t sound quite right for an Antillean Nighthawk. You can hear this bird on Macaulay Library cut 5904. It used to be classified as a Common Nighthawk, but as of this writing Macaulay’s got it labeled as an Antillean, and it’s certainly a confusing bird. Here are a couple of spectrograms:

To listen to the bird, click here.

Note that the bird gives a mix of short “pik” notes (the vertical lines on the spectrogram) and Common Nighthawk-like “peent” notes (the thicker blotches). By themselves, both of these elements suggest Common Nighthawk, as that species gives both calls. However, what seems odd is that the “piks” and the “peents” usually seem to merge into one, “pik pik pikpeent,” so that the typical rhythm ends up echoing that of the stereotypical chicken vocalization: “buk buk bukKAW.” By going through every recording labeled “Common Nighthawk,” I located nine cuts that included the “pik” call [1 2 3 4 5 6 7 8 9], usually alongside the “peent,” but none of them contain anything like this combination rhythm.

Here’s a typical Antillean Nighthawk call for comparison. It’s giving a relatively stereotyped “pit-i-mi-dick” of 2-6 notes in slightly decelerating series, the first element slightly longer than the others:

Typical Antillean Nighthawk call, Key Largo, Florida, 6/8/1962. Recording by Charles Sutherland. Macaulay Library #5903.

(click here to hear the bird)

As far as I know, Antillean Nighthawks do not give long series of individual “pik” notes like Common Nighthawks do, but I’d be interested to hear from anyone whose experience suggests otherwise.

As you can see, the “improper pit-i-mi-dick” bird is quite different from an Antillean. It may simply be a Common Nighthawk who is stumbling repeatedly over his words. But it sounds suspiciously odd to me, and given that it comes from the area of sympatry, a hybrid seems quite plausible. Interestingly, Sutherland mentions in his vocal notes that the call of this individual is not accompanied by the rapid flutter of wings that usually accompanies the primary call in both Common and Antillean Nighthawks. Who knows what significance that fact may have?

Comments?

The Alternate Song of Prothonotary Warbler

26 October 2009 Nathan Pieplow

Prothonotary Warbler, Chatham-Kent, Ontario, 5/4/2008. Photo by Gavan Watson (Creative Commons 2.0).

They don’t call it the Golden Swamp Warbler anymore, but name would still be apt, because the flame-yellow Prothonotary is a familiar sight in the swampy areas of southeastern North America. It’s a wonderful and evocative bird, one that even non-birders tend to notice when it perches or sings nearby. It’s one of the few warblers that nests in cavities, and it is the sole member of the genus Protonotaria.

In 2006, I joined a volunteer team in Cornell’s search for the Ivory-billed Woodpecker in the White River National Wildlife Refuge of Arkansas. During the two weeks I spent walking around in the untrammeled, uncampephiled wilderness, I had many spectacular close-up encounters with wildlife, but the most amazing was with a male Prothonotary Warbler. I was standing in hardwoods on the edge of a flooded swamp when the golden bird popped up over the water and began to sing. I switched on my microphone to record it, and suddenly it flew into a leafless sapling right over my head. I didn’t dare breath or move; I just kept the microphone running, hoping the bird would stay in the tree, hoping it would sing again. Sure enough, after a few minutes of foraging it began to belt out its familiar primary song: a fast monotone series of high clear upslurred whistles, not particularly musical, often transcribed as “sweet sweet sweet sweet sweet.”

Prothonotary Warbler primary song, Phillips County, Arkansas, 4/4/2006.

But then the bird did something even more extraordinary. It began to sing another song, one that was so faint that if the bird hadn’t been within five meters of me, I surely wouldn’t have heard it. And it was like nothing I’d ever heard from a Prothonotary before:

Alternate song of Prothonotary Warbler (same individual as above). Note that the song has three parts in a strict syntax AAAABBBBBBBCCC. The four calls at the end were not part of the song structure; I only heard such calls a few times, usually right before or after a song strophe. They appear to correspond to the typical flight call of the species, as recorded by Evans & O'Brien (2002).

I went to the literature to find out what I had recorded, and discovered this in Lisa J. Petit’s Birds of North America account (emphasis mine):

Second, less frequent song is sung primarily during interactions with females, often in aerial Flight Display. This extended song (Spector 1992) is longer and slightly more complex than primary song, beginning rapidly and slowing down at end: chwee-chwee-chwee- chwee, teer, teer, teer (LJP) or che-wee-che-wee-chee-chee, chee-chee-che-wee-che-wee (Walkinshaw 1979). Brewster (1878) described this song as resembling song of Canary (Serinus canaria), sung quietly, and consisting of “trills or water-notes interspersed.” Roberts (1899) referred to the song as beginning with the “usual rapid monotone” and ending with a “varied warble.” No sonograms of this song are known to exist.

“No sonograms known to exist,” of course, is the same thing as saying “no recordings known to exist.” Well, we fixed that, didn’t we?

Or did we? Upon reflection, the quote above demonstrates some of the difficulties inherent in trying to match old voice descriptions with modern recordings. Is this really the “alternate” song of males? After all, no female was present, and the bird wasn’t singing in flight. Could it be some other type of song? In her account, Petit also mentions two other potential candidate vocalizations, apparent juvenile subsong and female song:

Two separate observations by LJP during Jul 1985 of immature birds (sexes unknown, both in femalelike plumage-one color-banded, 45 d old; the other unbanded, assumed immature on basis of behavioral interactions with adult pair) singing quiet, raspy, oriolelike warble that did not resemble primary song of adults. Songs were 2-3 s long and were repeated 3-4 times. In Jun 1987, an unbanded female (apparently adult, since it was building nest) was heard to give same type of song, repeated 3 times.

I’m not sure how female song fits into the picture, or whether some of the observers cited in the first quote might have been describing it, but one thing is clear: What I recorded was not subsong. Subsong is given by juvenile birds between fall and spring as they practice for their big debut on a breeding territory. It’s poorly structured, with individual notes randomly mixed and rarely repeated, or repeated in garbled form. The song I recorded, on the other hand, was crystallized: the bird repeated it more than a dozen times, and each time it followed the exact same syntax pattern, with small variations in the exact number of notes A, B, and C, but absolutely no variation in their order, fine structure, or rate of delivery.

Many warblers have complex alternate songs. Some better-known examples include the “flight songs” of Ovenbird and Common Yellowthroat (for the latter, listen here, between the 21 and 24 second marks). Paul Driver’s got a neat recording of the extended song of Worm-eating Warbler, and Andrew Spencer has posted to Xeno-Canto what may be an alternate song of Black-and-White Warbler, although it may also be a type of call. Many of these song types are rarely heard and even more rarely recorded, so I’d love to hear of more examples.

Given that Prothonotary Warbler has attracted a good deal of research attention over the years, I would be surprised if nobody else had recorded the alternate song by now. If you have any information to share, please let me know. It’s probably worth writing up a note for publication in a journal.

Earbirding

Recording, identifying, and interpreting bird sounds

Browsed by
Category: Identification

New Crossbill Compendium

9 April 2010 Nathan Pieplow

Evening Grosbeak Call Types

21 March 2010 Nathan Pieplow

“Flight calls” vs. “Trills”

Type 1

Type 2

Type 3

Type 4

Type 5

Regions of Mystery

The Mysterious American Tree Sparrow

14 January 2010 Nathan Pieplow

How I Listen

11 December 2009 Nathan Pieplow

You Misidentified It Wrong

1 December 2009 Nathan Pieplow

White-breasted Nuthatch, Part Three

21 November 2009 Nathan Pieplow

Rapid Quanks

Hit-trills

White-breasted Nuthatch, Part Two

16 November 2009 Nathan Pieplow

Fast songs

White-breasted Nuthatch, Part One

10 November 2009 Nathan Pieplow

“Quank,” etc.

A Hybrid Nighthawk?

31 October 2009 Nathan Pieplow

The Alternate Song of Prothonotary Warbler

26 October 2009 Nathan Pieplow