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psychoacoustic illusions by birds

Subject: psychoacoustic illusions by birds
From: Dave Mellinger <>
Date: Thu, 27 Mar 2008 10:48:38 -0700
This is forwarded from Robert Yourell, 

Please include Mr. Yourell in your reply since he's not on Bioacoustics-L.

Do you know of anyone interested in the production of psychoacoustic illusions
by animals, particularly birds? I would like to know if anyone is familiar the
subject or with what I experienced when I was in Mexico (Chichen Itza).
I heard a bird that could, in a rapid sequence, imitate the sound of a larger
wingspread bird taking off toward me, and of twigs rattling as though a heavy
bird had just launched from a dry branch. I am assuming this is an evolutionary
adaptation to scare away predators of some kind. I know that the effectiveness
of psychoacoustic illusions depends quite a bit on the shape of the listener's
ears, so I'm surprised this illusion worked so well on me. I doubt if this
ability evolved to scare off humans.

I got the bird to make these sounds several times. It was very similar most
times, but a couple of times it wasn't quite as convincing or spirited. The
first time I heard it, I spun around to face the big bird coming at me, but
there was only a little black bird (perhaps seven inches long) sitting in a tree
about thirty feet away.

I've never come across any information on an animal using psychoacoustics to
create an illusion.

I'd appreciate any contacts or ideas on this. I'm not a bird watcher, but I am
interested in psychoacoustics because of recordings that I make. This is why I knew what I was hearing. I have heard psychoacoustic
illusions of various kinds, but all of these were produced with software, not

Regards, Bob
Robert A. Yourell

Preparing people for challenges
"Sounds for Inner Space(tm)"
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