I know this is an old topic, but, to my knowledge it has never been
conclusively settled.
Having read Louis Baptista's work (http://tinyurl.com/ysl4l8) and many,
many others over the years, I am still unconvinced myself how this sound is=
made. Most of the recordings I have of the sound have a distinct wing trill=
preceding them. That trill is the sound of wings building up speed before
the pullout at the bottom of the dive. But I also have several samples that=
lack that precursor and which were recorded without seeing the bird. That
in itself means little, but the interesting thing is that both types of
samples often show two distinct frequency bands at the same instant. (see
http://tinyurl.com/2xy3ve) - hear the sample at
http://tinyurl.com/2xy3ve.This is something we commonly see in oscine
Passerines, since they have two syrinxes, but not in non-oscines. The two
bands may indicate more complex vocalizations that we expect in hummers,
but it may also indicate that there are two different places generating the=
sound (like two different tail feathers or groups of feathers). It seems
unlikely to me that these two bands come from vocalizations...but maybe...
I'd be interested in hearing your thoughts and experiences with this.
Has anyone ever seen an Anna's Hummingbird make this sound while sitting
stationary?
Does anyone know of any high-speed movies of the dive and sound being made?
Other thoughts about how we could conclusively settle this? Or do most
believe that Baptista's work settles it?
Doug
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Doug Von Gausig
Natural Sounds and Photos at:
http://naturesongs.com
More Photos at:
http://www.criticaleyephoto.com
Clarkdale, Central Arizona, USA
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