In other words, the types of abnormalities that the authors describe as analogous to stuttering are in fact analogous to far more complete abnormalities in human language. Finally, it is wise to remember that human beings produce speech with a mechanism that is qualitatively very different from that used by birds in singing. Birds have a syrinx, which is somewhat like a larynx, but they have two of them, one on each side in the bronchial tubes. This can easily be appreciated by playing the birdsong at a slower speed than it was recorded at, and the difference becomes instantly clear. The human system, on the other hand, involves upper airway articulations that stop and start the flow of air, introduce additional sounds, and modulate resonance.
Birds have none of that.
So, given that they have a very different system used for a very different purpose, the analogy falls on extremely shaky grounds. Oh yes, I forgot to mention that the acquisition of birdsong, although it has the convergent similarities that Marler noticed, is really quite different in most of its aspects. Chomskian acquisition devices granted, there is substantial learning of langauge, and in the later stages, language is actively taught to human children, and the whole process takes, as we know, a considerable investment of time, even though it may seem shorter than we would have expected. Thanks for contacting me. Let me address several points.