An Odd-Sounding Chickadee

This afternoon, I was birding at University of Guelph’s Arboretum. At one of the feeders, I heard a rather peculiar sounding black-capped chickadee. Here is a sound clip I took and uploaded to the Macaulay Library.

This is one of the calls of the complex vocal repertoire of the black-capped chickadees. This chicka-dee-dee call is usually made when they are alarmed. What I found interesting about this individual’s call was the dee-dee part. In the field, it sounded “not as full” to me, if that makes sense. As a reference, take a listen to this sound file of a black-capped chickadee (skip to roughly -24.000 seconds). Compared to the chickadee I heard, the dee-dee-dee sounds fuller and richer in this reference sound.

Recently, I have been getting into reading and analyzing bird sound spectrograms. This odd-sounding chickadee gave me a good opportunity to see if there was any difference in spectrograms between it and the calls I usually here, the “richer/fuller” calls.

The Macaulay Library website generates a spectrogram for any sound clip you upload. In my clip that I linked above, this is that gray-scale line plot that plays when you play the sound. However, I wanted to generate my own. Using the seewave library in R, I created two spectrograms: one for my odd chickadee, and one for the reference chickadee in that sound file I linked.

Here are the results. The first plot is my odd sounding chickadee, the second plot is the reference call.

bcch-callbcch-call-ref

Let’s first break down what we’re seeing here. The first two or three “curvy” lines that fall between 5-10 kHz of frequency is the chicka part of the call, and the rest of the horizontal lines that fall between 0-5 kHz frequency is the dee-dee-dee part of the song.

By inspecting both plots, I think you can see a clear difference in dee-dee part of the song, which is what I suspected. In my recording, there is only one clear spectral line present at ~4 kHz, with two very faint spectral lines appearing at ~2 kHz and ~5 kHz. Compare that to the reference file where there is essentially a stack of spectral lines between 2-5 kHz. This stack would create a richer, fuller sound which is what I usually hear in chickadee calls. Compare that to the one spectral line in my chickadee, and I think that’s a good explanation for the “emptiness” I heard in the dee-dees of that chickadee.

Black-capped chickadees are known to have rather complex vocalizations, variations of which can often be picked up in these spectrograms. This is just the first time I’ve heard a chickadee like this, and I thought it was super interesting to plot the sound. I’m not entirely sure if this can be chalked up to regular vocal variation, a young chickadee still learning its call, or something entirely different, but I’ll definitely be doing some research over the next few days to investigate this!

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