Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!ames!uhccux!mikeb
From: mikeb@uhccux.uhcc.Hawaii.Edu (Mike Burger)
Newsgroups: rec.birds
Subject: Head bobbing
Keywords: head bobbing
Message-ID: <8886@uhccux.uhcc.Hawaii.Edu>
Date: 6 Aug 90 18:45:31 GMT
Distribution: usa
Organization: University of Hawaii
Lines: 19


	The idea of visual pigment bleaching is interesting.  Maybe the
bird is trying to keep its head stationary on purpose to promote bleaching.
In the frog, for instance, it uses an apparent visual bleaching as a
protection.  It goes blind sitting still and only notices things which move.
One can imagine anything that moved in his visual field standing out
against a black background.
	Perhaps birds sometimes make use of this idea.  When walking
on the ground, using head bobbing to keep the world stationary, only
things changing their perspective significantly as the bird moves would
be "seen".  The background clutter would vanish, perhaps revealing the
cat which just moved closer.
	Then again maybe birds just bob their heads because it feels
good :-)

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Mike Burger   Department of Chemistry     |      2545 The Mall      |
BITNET:       MIKEB@UHCCUX.bitnet         |  University  of Hawaii  |
INTERNET:     mike@helium.chem.hawaii.edu | Honolulu, Hawaii, 96822 |