Animated GIF: quintessential genre of the modern internet. A good proportion of the web is devoted to these short, silent looping video clips, mostly in the service of slapstick humor. But GIFs have significant educational potential as well, especially when it comes to the visualization of patterns — which is what this whole website is all about.
Ornithologists use the term variety to describe the pattern of delivery of a bird song over time. Some individual birds sing only a single song over and over (no variety). A bird that can sing multiple songs might choose to sing one for a while before switching (eventual variety), or it might switch constantly (immediate variety).
In the field, it can take many minutes of listening to determine a bird’s pattern. Animated GIFs of spectrograms can condense all this listening into just a few seconds of looping video:
(songtypes repeated several
times before switching)
In each GIF above, the spectrogram of a single bird song appears on the screen for one fifth of a second. It is then replaced by the spectrogram of the next song by the same bird. After a couple dozen songs, the animation loops back to the beginning.
Seeing song similarities (and differences)
As all naturalists know, the pieces of nature rarely fit into neat categories — and so it’s no surprise that the three categories of variety above are inadequate for describing the more complex patterns of variation found in many bird songs. A GIF, though, might be up to the task.
Take these 18 songs from a Vesper Sparrow:
Note that the level of variety at the beginning of each song is completely different from the level of variety at the end. Each song starts with the same 3 (rarely 4) downslurred whistles, followed by the same rapid series of vertical notes (the number varying from 5 to 7). After that, variety increases dramatically. The middle section irregularly alternates between two different patterns, and the ending switches even more frequently, between at least three different motifs.
This type of cascading variety is typical of Vesper Sparrows. The opening notes tend to vary little within an individual, but by the end of the song, variation is tremendous. Perhaps this allows the sparrows to “have it both ways” — that is, to simultaneously send two conflicting messages to the listener. The stereotyped opening satisfies their need to identify themselves unambiguously to a potential mate or rival (“I am a typical Vesper Sparrow!”), while the jazzy ending allows them to show off their improvisational virtuosity (“I’m not your ordinary Vesper Sparrow!”).
I’m fascinated by the potential for GIF visualization… perhaps you’ll see more animated spectrograms on this blog in the future.