Coiled Trachea
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Most songbirds (and humans) avoid the problem of the bugle players limited range of notes because they sing in a range that's mostly below the resonant frequencies of their airways. (Human sopranos do get up into a range where they have to alter their airways so that resonances match the note they're singing, and some birds run into a similar situation high in their ranges.)

But that doesn't mean that the airway doesn't affect sung notes. It just means that, in most singing, it affects the overtones of the voice much more than the fundamental note. To understand that, we'll need to use the human voice as our analogy to bird singing. Still, there are a couple of other aspects of our bugle analogy that can help us understand some aspects of birdsong:

  • The bugle's airway is coiled up. That makes the modern bugle much more compact than the straight hunting horn. And some birds use the same strategy. The sandhill crane has a complete loop of airway in its keeled breastbone. The whooping crane goes even further by having two complete loops of airway in its breastbone.
  • And something as apparently simple as the flared bell on a bugle changes the resonances of the bugle's airway to create a higher, sweeter sound. Both birds and humans can alter their airways is more complex ways by moving their heads, mouths, tongues, and lips or beak.

Chris Tenney recorded the chorus of sandhill cranes at the Los Banos National Wildlife Refuge. I found recordings of the guard and unison calls of the sandhill crane from the International Cranes Foundation website.

The unison and alert-guard calls of the whooping crane are from the Bring Back the Cranes media page. The final recording of the whooping cranes calls is from the CD collection Western Bird Songs produced by the Cornell Laboratory of Ornithology for the Peterson Field Guides series.

The buzzing lips and the tones of the lengths of PVC pipe are from the brass acoustics page of Joe Wolfe's wonderful music acoustics website at The University of New South Wales.