What does this mean?
"These sonograms are remarkably different from other sounds, as if birds “draw” with sound something that’s flying backwards in time."
Basically, all sounds that you hear are composed of many layered sine waves of different frequencies and intensities. The graphs in the post are spectrograms, which graph those frequencies over time. The Y axis represents pitch, the X axis represents time, and the brightness at any given point represents how loud that particular frequency was at that particular time.
Most sounds, even seemingly simple ones, look very complex on a sonogram, like a smudged pen stroke. The images of different instruments below demonstrate this; these are all very complex sounds, even though we only hear it as a single note being played. The voice one is one of my favorites, because it shows just how weird and complicated everyday sounds can get.
But bird songs are different; on a sonogram, they appear as a single line. The complexity of the bird songs here comes from the fact that they're taking a single sine wave and changing the pitch over time. Where most sounds look like a complex mix of smudged paint strokes, bird songs look like a single, precise, bouncing stroke.
Which is akin to dragging a single finger across different piano keys. Only a single frequency, or note, played at a time. This is common among songbirds.
Contrast that with the sound of a crow. The sonogram is much more broadband in signature. This is akin to mashing a bunch of keys on a piano all at the same time. Many frequencies present at simultaneously.
I think there's a key difference.
Assuming this is the spectrogram of single note being played on the Piano (https://soundshader.github.io/hss/gallery/piano/2.jpg) (which I can't be certain of, since the audio sample wasn't provided). Seems like a single piano note fires on multiple frequencies, and our ear 'aggregates' them so we hear it as a single note.
Songbird belts out a single frequency at each point in time. We still hear a single note but there's nothing to aggregate.
At least that's my interpretation of the parent comments. Again, can't be sure.
Crows, in the morning, seem to be broadcasting work gang related information, organising their crew to go and harvest certain regions, then report back on the yield.
If songbirds are courting, and hence broadcasting different information, for different purposes, I wonder if some generalisable differences might be apparent in the receiving birds brains.
https://www.xeno-canto.org/species/Dromaius-novaehollandiae?...
Are birds sending specific data packets eg weather, food prospecting geocoordinates? Or are they entertainers like Frank Sinatra or Dolly Parton?
And could we decipher the language by studying data in context eg food hunts, mating rituals, predator warnings?
What might Claude Shannon make of these spectrograms?
The short of it is that most natural sounds product a root tone plus a varying amount of related tones above it. Our ears hear the root tone, and the other tones above it are what give the sound its uniqueness. That's why a guitar, a clarinet and 3 singers can produce the same note while sounding distinct.
Birds seem to produce a natural sound without a lot of the related tones above it. Their sound is, relatively speaking, much purer than most other natural sounds. That's very unique.