Start Using Spectrograms to ’Read’ Bird Songs and Calls

Editor’s Note: There's a lot to look forward to in spring, including the welcomed hullabaloo of birdsong. The sheer volume of songs and calls can often feel overwhelming for birders, but these sounds offer both an opportunity and a challenge. Follow along with our birding-by-ear series to learn how to better ID birds through their vocalizations. To catch up, be sure to check out part 1, part 2, part 3, part 4, part 6, part 7, and part 8. 

In part 5, “Earbirding” master Nathan Pieplow explores the cool new frontier of converting sounds into spectrograms. The resulting visuals can be a powerful tool for studying some of the most mysterious parts of a bird's language, he says. So what are you waiting for? Let's interpret some spectrograms. 

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Some birders can hear the magic in a bird’s voice. Others need to see it to believe it.

I was out one day with Ted Floyd, editor of Birding magazine, when a warbler flew across the path behind him. As it swooped past his head, it emitted a single sharp chip note. “Oh!” he said, without turning around, “Black-throated Green!” It was the first time I’d ever seen anyone correctly identify a warbler from its chip alone.

Unlike Floyd, my ears aren’t magical, and my brain doesn’t recall calls and songs well. I need pictures. Lucky for me, modern technology makes it easy to take pictures of sounds by way of spectrograms: computer-generated graphs that show the basic shape of an audio wave and how its frequencies change over time. Sounds only last a moment before they’re gone, but spectrograms make it possible to capture them as a permanent visual resource.

Reading spectrograms is like reading sheet music; the song runs from left to right, with the high-pitched notes near the top and the low-pitched notes farther below. Unlike human compositions, however, the horizontal width of each note on a spectrogram determines how long it lasts—anywhere from a few seconds to a fraction of one. Meanwhile, the shape indicates quality. A whistle, for instance, looks like a single, nearly horizontal line, while a nasal sound produces a bunch of horizontal lines stacked on top of one another. Check out these two spectrograms to compare the whistled song of the Black-capped Chickadee to the nasally notes of the Red-breasted Nuthatch.

Think of spectrograms as the SparkNotes of birding by ear. They’ll help you study, but they won’t get you a perfect score. They do, however, teach you to listen better, which ultimately makes you a better birder. A spectrogram can reveal little subtleties in a sound that you may not have noticed before. For example, notice the tiny break in the middle of the Black-capped Chickadee’s second note in the graph above. Now, play the audio. See how the space makes the second note sound slightly double-syllabled?

Before I saw it on a spectrogram, I thought the chickadee’s song only had two parts, and transcribed the song as fee bee. But now that I know the break exists, I often hear three syllables in the song. It sounds more like hey sweetie to me. It’s just another example of how spectrograms let you use your eyes to focus your ears on the finer details in sounds.

So how do you generate your own spectrograms in the field? There’s an app for that, of course. The best one I’ve used on my Android is the SpectralPro Analyzer, which costs $4.49. The iPhone has an even better option: SpectrumView, which is free for download, but offers extra features at a price. If you download either of these apps, make sure to change the settings to a sample rate of 22,000 Hz and a black-on-white color scheme—the ideal parameters for graphing bird sounds. In Android’s SpectralPro, I also recommend the “fast” update speed and “scroll” viewing option. Both apps allow you to freeze certain parts of the spectrogram and save it to your phone for future use. SpectrumView for the iPhone also allows you to record audio. The biggest drawback to the technology is that the bird has to be loud and close for a clean visualization, but adding an external microphone like the RØDE VideoMic Me will raise the quality of the clips.

Once you’ve created your own spectrograms, you can use my new book, the Peterson Field Guide to Bird Sounds of Eastern North America, to work out the IDs. The index in the back will help you group the graphs by shape and sound type. Let’s try one right now for fun.

First, listen:

This mystery song consists of short phrases, separated by pauses that are more than a second long. The phrases never repeat: Each one is unique to the ones before it. According to the index of my field guide, the pattern falls under the category of “mostly different single phrases.” There are a few vireos and flycatchers listed on that page. If you flip through those species in the book and match your spectrogram to the pictures in the book, you’ll arrive at the correct identification: Red-eyed Vireo.

In the end, a spectrogram acts as a species’ signature. Each one may have minor variations, but breaking down the overall pattern should give you a good idea of what bird you’re listening to. Try it, and it won’t be long before you can impress your friends with your ability to identify sounds on sight.