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The Gargling Chickadees

The Gargling Chickadees

Chestnut-backed Chickadee, Vancouver, BC, 11/20/2010. Photo by Sean McCann (Creative Commons 2.0).

What do chickadees sound like?  Why, everybody knows they say “chick-a-dee-dee-dee,” of course.

These “chick-a-dee-dee-dees” are what many people (and many books) describe as the “calls” — not to be confused with the “songs,” which are usually understood to be the high clear whistled tunes sung by males in a territorial mood:

All chickadee species give “chick-a-dee” calls, but only three of them — Black-capped, Carolina, and Mountain  — have whistled songs.  Since these three species are the most widespread and familiar North American chickadees, many people tend to judge other chickadees by their standard.  “Lacks whistled song,” many field guides say of Mexican, Chestnut-backed, Boreal, and Gray-headed Chickadees.  “No song,” say others, or simply “song unknown.”

But the many researchers who have studied chickadee vocalizations for decades might disagree.  As far back as 1981, Millicent Ficken pointed out that an often-overlooked chickadee vocalization called the gargle may actually fulfill more of the traditional “song” functions than the whistled songs.

Unlike whistled songs, gargles can be heard from all North American chickadee species.  Like traditional songs, gargles are learned; Ficken notes that captive Black-capped Chickadee hatchlings do not develop proper gargles in the absence of an adult tutor.   Individual birds typically produce several different types of gargles, forming a repertoire.  In most or all species, the gargles are given primarily by males and  associated with dominance establishment and territorial defense.  They are extremely complex, being made up of many different note types, often with trills and repeated motifs.

For all these reasons, in the species that don’t also whistle, the gargles can be considered “the song”:

Although some field guides may frame them as the outliers, the chickadee species above are not the unusual ones when it comes to the traditional song/call distinction.  It’s the whistling chickadees that are unusual, because they have two different kinds of songs — not only whistles, but gargles as well:

The whistling chickadees are a perfect example of how the original “song/call” distinction fails to hold up in many species.  Not only can the whistle and the gargle both be called “songs,” but even the “chick-a-dee” calls could be considered songs by some criteria.  We should always be suspicious of the many generalizations about birds that we draw from the most common, widespread, and familiar species — remember, they may be the unusual ones.

 

Splitting Mountain Chickadee

Splitting Mountain Chickadee

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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