[Tweeters] A new bird behavior discovery - for me

[Mark Walton via Tweeters]

I'm a neuroscientist and my research interests involve how the brain
controls eye and head movements so this is getting close to my area of
study.  The ability to hold the head steady in space, even while the body
is moving, is referred to as the vestibulocollic reflex. Basically, the
organs of the inner ear (the otoliths and semicircular canals) detect head
acceleration. The brain then sends a copy of this head acceleration signal
to the neck muscles, which causes them to make an equal and opposite head
movement. This effectively cancels out any short-duration unplanned
movement of the head in space. If the head movement was intentional, the
brain sends a copy of that voluntary movement command to the brain areas
responsible for the vestibulocollic reflex, so that the reflex can be
temporarily cancelled.

This reflex is one of several "gaze stabilization reflexes". To understand
why these are necessary, think about the times when you've seen a news
camera operator running after the action, while still filming. The camera
is moving all over the place while the person runs, and you can't see much
of anything. This is what would happen to our vision without these gaze
stabilization reflexes. In graduate school, one of my professors told of a
man who had suffered brain damage that wiped out one of these reflexes
(vestibulo-ocular reflex, which causes the eyes to rotate in the opposite
direction from an unplanned head movement). The man could not even read a
book without wedging his head into a corner of the bedroom, because even
the tiny head movements that we constantly make were enough to make his
vision too "jiggly" to read. The vestibulocollic reflex, and the
vestibulo-ocular reflex, are the reason that you don't become functionally
blind while you're dancing.

So many species, including humans, have this same vestibulocollic reflex,
to stabilize the head position in space during movement. Obviously, this
gaze stabilization is even more crucial if you're a bird perched on a
moving branch, or making a sharp turn in flight. So, not surprisingly, the
vestibulocollic reflex is extremely strong in birds. Another reason that it
is so strong in birds is that they have a much smaller range of eye
movements than humans do, which means they have to rely more heavily on the
vestibulocollic reflex, and less on the vestibulo-ocular reflex.


Mark Walton


Ar Sath 27 Iúil 2024 ag 16:44, scríobh Dennis Paulson via Tweeters <
tweeters at u.washington.edu>:


> Jim, it seems to me that birds are able to do that, hold their heads

> steady as they move their bodies in different positions. That long,

> flexible neck facilitates that greatly. Watch a coot or pigeon moving and

> note their bobbing head. They are holding their head still, presumably for

> better vision, as the body moves under it.

>

> Dennis Paulson

> Seattle

>

> > On Jul 27, 2024, at 12:41 PM, Jim Betz via Tweeters <

> tweeters at u.washington.edu> wrote:

> >

> > Hi,

> >

> >   I've gone to Channel Drive (near La Conner) several times this week.

> I was attempting to

> >

> > get a picture of a swallow in flight and although a barely useful image

> it does show

> >

> > something I didn't know about.  The swallow was making one of those

> tight, horizontal

> >

> > turns.  The wings, tail, and body were all turned almost 90 degrees

> (think "vertical").

> >

> >   But the HEAD was still locked in the normal/horizontal orientation.  A

> subsequent

> >

> > photo of a flock of Western Sandpipers showed the same thing. Perhaps

> this is a

> >

> > common bird behavior that I just haven't noticed before?

>      Fun!!!   - Jim

> >

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