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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.


Hearing Loss and Bird Sounds

Hearing Loss and Bird Sounds

Happy birthday Earbirding! Photo by Theresa Thompson (Creative Commons 2.0).

In honor of Earbirding’s first birthday (yes, we went live one year ago today), I’m posting on the topic of getting older — and losing your hearing as you age.

Age-related hearing loss, or presbycusis, happens to almost everyone to some degree, although it tends to be more severe among men, and susceptibility can run in families.  It runs in my family, for better or for worse — even though I’m not yet 35, when I go birding with my friend Walter, he can detect chickadees by ear at twice the distance at which I can hear them.  The other day, he and I watched a Blue-gray Gnatcatcher vocalizing at a distance of about 50 meters.  He could hear it distinctly; I watched the bird’s bill opening and closing in silence.

Age-related hearing loss tends to affect high frequencies first, so that the upper frequency limit of a person’s hearing tends to decrease over time.  A European inventor exploited this fact to create a device called “the Mosquito,” a type of sonic “youth repellent” that keeps bus stations and storefronts free of loitering juvenile delinquents by emitting a piercing high-pitched frequency that only young people can hear.  (In retaliation, young people have converted the “Mosquito’s” buzz into a cell phone ringtone that their aging teachers can’t hear when it rings in class.)

In the past I’ve written about some corrective technologies for birding by ear.  Today I’d like to give those of you with perfect ears a chance to experience partial hearing loss.  It’s easy to filter out the high frequencies of bird sounds to get an idea of what you would hear if they were missing.  Some songs, like those of the Golden-crowned Kinglet, would disappear entirely.  Click on the link to test your hearing — if you can still hear the kinglet’s song, then your ears are pretty good.  I can still hear high-pitched songs like this just fine, as long as they are at close range.

But there are other ways that hearing loss can affect our perception of sounds besides eliminating the songs entirely.

Losing Songs in Pieces

Some bird sounds are composed of both high- and low-pitched notes, so that those with presbycusis may hear parts of the sound and not others.  A great example is the typical “fee-bee, fee-bay” song of the Carolina Chickadee, which is one of the best ways to distinguish it from the lookalike Black-capped Chickadee, which sings a simple “fee bee.”  The complete song is easy to identify:

Carolina Chickadee song, McCurtain County, OK, 3/23/2008.

But those with an upper hearing threshold of 6 kHz, which constitutes only a moderate hearing loss, will hear just the two lower notes:

Same recording as above, with all frequencies above 6 kHz filtered out.

And that makes it sound much more like the Black-capped Chickadee:

Black-capped Chickadee song. Larimer County, CO, 5/20/2008

Hearing Loss and Tone Quality

I used to be skeptical that presbycusis could affect the tone quality of sounds, but in some cases it can, especially if the sound is highly nasal.

Here’s a quick reminder in case it’s been a while since you visited the page that explains the nasality of sounds.  To have a nasal tone quality, a sound must be harmonically complex.  Such sounds appear on the spectrogram as vertical stacks of lines.  If the darkest lines in the stack are at the bottom, the quality of the sound won’t be nasal at all.  The higher the darkness climbs, the more nasal the sound.  Thus, the call of the California Gnatcatcher sounds intensely nasal:

California Gnatcatcher, Riverside County, CA, 3/22/2009.

Here’s the same sound, filtered above 6 kHz.  Note that the basic sound remains the same, but the quality changes slightly.  However, I’d still call it “nasal.”

Same sound as above, filtered above 6 kHz.

Here’s the sound filtered about 3.5 kHz.  (This is about the same level of high-frequency filtering forced on all of us by our telephones.  If you’ve ever wondered why people’s voices sound slightly different over the phone, it’s because the phone companies decided long ago that those higher pitches were mostly unnecessary to human speech, so they simply aren’t transmitted.)  This version of the call maintains its basic pitch (because pitch is determined by the spacing between the partials), but the quality is muted, duller, and less nasal.

Same sound, filtered above 3.5 kHz.