Position a song in the center of each sonogram so we can compare them. It is easy to see that the
one above is shorter, slower, and lower. The rest of the text is below.
This is an example of two common species that are easy to tell apart visually, but not so easy by ear. There are numerous other examples,
but this is one of the most problematic. This Chipping Sparrow song is high and dry, which is what you want it to be. The Pine
Warbler song is low and slow, comparatively. "Slow" means the spaces between notes are longer. By the way, both of these songs qualify as trills.
When it's slow enough for you to count the notes, it's a series. I don't know about you, but I can't count the notes of that
Pine Warblers usually sound something like this; the trills are somewhat muscial. Each of the Chipping Sparrow notes is so
steep (i.e., the pace of frequency change is great) that your brain doesn't resolve the frequency change and it sounds like a click. This is despite
the fact that the individual notes of this bird have exactly the same shape as our Pine Warbler notes. Their steepness makes
the trill sound "dry." That's if the Chipping Sparrow is being nice. Sometimes they slip down into the Pine Warbler register, and can sound
I have my own hypothesis about that. Ornithologists in Oregon taught me that Chipping Sparrows can sound very similar
to Dark-eyed Juncos. They thought that the sparrows were adopting songs from the juncos. Maybe the same thing is going on in the east, i.e., they
adopt songs from Pine Warblers. But Chipping Sparrows usually have only one song-type.
You'd think they would do better with their own species sounding like a Chipping Sparrow. So, the jury is out on the song-adoption
hypothesis, but it does raise another possibility. Pine Warblers do have more than one song-type per individual, so if you hear a bird switch it should
be the warbler, right? I'd take a look to be sure.