> been picked up). He also mentioned that the hypothesis that what is
> being
> recorded is the harmonics of audible calls.
>
The Anabat detector usually only picks up the dominant harmonic, & I
suspect that in birds this would be the audible one?? .. but it remains
a possibility.
> We also discussed why Nightjars would need ultrasonic calls. Oilbirds
> (from
> S. America, nightjar relatives) and our own White-rumped SWift use
> them, but
> they nest in pitch-dark caves and need echo-location to find their
> nests.
>
I don't know about Oilbirds, but I believe swiftlets use audible
echolocation, not ultrasound. Some cave-roosting fruit-bats (Rousettus)
also use audible echolocation (basically tongue clicking), in contrast
to the sophisticated ultrasonic echolocation of microbats. Sound
doesn't have to be ultrasonic to be useful for echolocation.
> I guess sonagrams are required before anything else.
>
Indeed. I'm keen to see an "Anagraph" of this sound, & Glen tells me
that a tape of the call is headed my way. I'll report back to the group
in due course.
Lawrie Conole
Geelong, Victoria, Australia
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