Would you like to identify birds by the sounds they make, but just can't get the hang of it? If so, you might be interested in the visual approach, with sonograms. Here is an introduction to the topic.
You can play the sound again and again. Notice the long pure note depicted by the flat line from 0.5 to 1.0 seconds on the horizontal axis. It is easy to see that the flatness of the line represents uniformity of pitch. Let's call that pure tone a "whistle."
The second half of the song is a "slow trill," slow enough that you can count each repeated phrase, a trill because it is a series of repeated short phrases. The sonogram shows us that each phrase is a slur, a sweep from a high to a low frequency, but we don't really hear that. Each phrase just sounds like a "chirp" or even a "click."
After listening, did you recognize the song? The basic pattern of a whistle followed by a trill is used by a number of bird species worldwide. The two main practitioners of this pattern in the southeastern US are the Eastern Towhee and the Bachman's Sparrow. Which one is it? If you are in doubt, click here for another clue. This cut takes over a minute to play.
Why did we have to listen to a whole minute of singing? Because there is additional information about the species of the singer in the sequence of songs he sings. If each succeeding song is different from the previous one, bird musicologists call that "immediate variety." Bachman's Sparrows usually sing with immediate variety, while Eastern Towhees usually sing with "eventual variety," that is, they repeat the same "song-type" a number of times before switching to another variant. The many song-types of Bachman's Sparrow do differ consistently from the many song-types of the Eastern Towhee, but if you're not sure which you're listening to, noting the repetitiveness of the singer (serenade syntax) can help you nail the identification.
Click the link above again to see if you can detect transitions from one song-type to another. Is variety immediate? If it's hard to keep up with what you've already heard, try listening while looking at the moving sonogram below, courtesy of eBird.
Now, that's all well and good, but one of the wonderful things about sonograms is that they can be used to freeze time. The sound of interest occurred in the past, yet we still have access to it. Just as a page in a book is the freezing in time of a speaking voice, a sonogram can be used to lay out in space a temporal sequence of sounds. That's just what a musical score does. So, take a look below at the entire sequence of songs in our Bachman's serenade, frozen in time, so we can examine it at our leisure. Look for patterns in this "score." And you can listen, too, by clicking it. It won't move, but you can follow the sequence of sounds on the score with your finger.
All these interesting observations, which are accurate descriptions of the evolved communication system of the Bachman's Sparrow, are accessible to us because of Sonograms. So, how can we use them to learn to identify bird songs?
The following two books use sonograms extensively:
PDF of Birding by Ear, Visually, Part 1: Birding Acoustics
PDF of
Birding by Ear, Visually, Part 2: Syntax
As part of the article on syntax for Birding (see above), I created three prototype spreads for a "field guide" to sonograms. You can review them by clicking the links below. Clicking on a sonogram will play the specific sound under the cursor. The Empidonax page, for example, is linked to 30 separate sound clips.
Owls that Toot or Trill | Western Empids | Melospiza Sparrows and Allies |
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