No need to speculate:
Dooling, R.J. and Popper, A.N. (2000). Hearing in birds and reptiles: An
overview. In: R.J. Dooling, A.N. Popper, and R.R. Fay (eds). Comparative
Hearing: Birds and Reptiles. (pp. 1-12). New York: Springer-Verlag.
On Behalf Of Julian
Sent: 31. marts 2008 15:15
Subject: Re: songbird audiograms
>Michael Stocker wrote:
>"We could infer that they do use these sounds for something which
>involves their being able to hear them ...."
>To which Martin Braun replied:
>"This may not always be true. Imagine the following scenario:
>A bird is deaf above 6 kHz. If this bird has sound components
>around 10-12 kHz in its calls, it cannot hear these components and it
>is thus unable to influence its voice organs to reduce or even
>Martin, imagine this scenario:
>A bird can't hear above 6 kHz but it produces sounds above that
>frequency in its calls. There should probably be other costs the bird
>"wants" to cut out other than hearing the sounds. Costs of producing
>them (energy, motor coordination at syrinx, etc.) so probably they
>are "taken away" in evolution. But even if they are produced as a
>"side-effect" by some individuals (are, in a certain way, "neutral"
>to them in terms of costs), why if a predator locates those
>individuals using the above 6 kHz frequencies?
>So, I agree that we have to have factual proofs of the audition
>range of a species, because speculation could be right or wrong in
>any of the "two" senses we are discussing about. But, my guess is
>that in most cases individuals of any species can hear AT LEAST the
>frequency range of their own emissions.
It would be interesting to see empirical data concerning this
relation. Since there is a structural coupling between different
aspects of sound production, and thus between the resulting spectral
bands, the case may be more complicated. It is not even necessary
that they are "cost neutral", since selection does not operate on
energy exchange directly. An insect also produces sounds which are by
no means without cost but which are side effects of wing motion, or
sound production. But I'd be curious to hear opinions.