We can demonstrate that zebra finch birdsong, in some birds, contains iterative sequencies that are similar to the part-word repetitions of stuttering. What we can not is aemotional angst. I hope that we can spend more time discussing this at the IFa. Comments Most of the points you mention as justifying a comparison between birdsong and human speech production are a product of genetic convergence, that is, it is remarkable that they occur at all, but they most likely do not mean that the two systems are comparable. But the point of comparison that you say is most important, that birdsong is spectrally complex, as speech is, is quite wrong.
Birdsong is spectrally simple.
It is simply a tone, varied rapidly in its temporal characteristic, so rapidly that it sounds as though it is spectrally complex, but in fact it is nearly a pure tone. There are of course some harmonics, attributable to the air spaces in the bird's upper airway, and there is even some variation in these harmonics during the song, but the harmonics vary ONLY in correlation with the vocal tone and are a byproduct of its production. There is absolutely no harmonic, or spectral variation in birdsong that contributes to the song, in the way that human articulation does. In other words, the harmonic variations that occur in birdsong are not part of the signal-production as they are in humans, so one would have to assume that the neural organization of motor control is also vastly different in the two species. And of course, as I pointed out in my previous post, the function of birdsong is also vastly different, and the physiology of birdsong production is vastly different.