> As promised in a my previous mail, I uploaded a file on Soundcloud
> a true song duet between a Blackbird, Turdus merula, and a Green
> frog, Rana esculenta.
> I suspect that the frog reacts to the song of the blackbird how it
> would reacts to any sound of loud intensity, because it happened to
> me to hear frogs singing as soon as it happens a loud noise such as
> a passing train or a plane not far.
I suspected that my theory that the bird song and frog frequencies
were matching hadn't worked until I took power spectrums from the
starts of each call.
The frog has a clear peak at 2150 Hz, below most of the blackbird
song, but almost exactly 200 ms before each frog croak, the blackbird
peaked at that frequency. The frog only missed one call but was
perhaps still listening out when the blackbird sang early. Listen to
the rercording at 1/5th speed and you can hear this at around 430Hz.
I think we can say that the frog is responding to the main frequency
in its croak, wherever it comes from.
A frog does not have vocal chords, so it can only make a frequency
dependant sound with a resonant cavity. Our ears cannot distinguish
this frequency and only hear a croak, but the frog seems to be
responding to its own resonant cavity frequency. Presumable this keeps
different species apart.
We learn all sorts of stuff on this list, like the word "sintony". :-)
In this case it actually means "same frequency".
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce