[Tweeters] Motion in Birds

[Mark Walton via Tweeters]

My immediate thought/speculation about the starling murmuration thing is
that it sounds like something that might be a result of the fact that it
takes any brain a certain amount of time to process visual information from
the eyes, determine the appropriate movements to react to what was seen,
and then compute the exact amount of contraction needed for each muscle to
execute the planned action. I would guess that visuo-motor reaction times
in birds are probably MUCH faster than they are in humans but it certainly
wouldn't be instantaneous. If each starling is reacting to the movements of
the most nearby starlings then, for a large flock, these very small
processing delays would add up to something that would be noticeable to us.
The end result would be that birds that are far away from each other in the
flock make direction changes at different times, resulting in the flock
rapidly changing shape.

I'm thinking it might be the same kind of phenomenon as when you're driving
in heavy traffic and you're stopped at a red light with 20 cars in front of
you. The light turns green and it feels like it takes forever for the car
in front of you to get moving - even though every single driver is reacting
fairly quickly. It's just that the visuo-motor processing time ends up
being rather long when the small processing delays for 20 people get added
up.

In a flock of birds I would guess that it would also serve the important
function of possibly confusing a predator. So, maybe it's a case of the
laws of physics and chemistry imposing delays that happen to benefit the
birds?

As an interesting aside, there are some situations in which these
processing delays pose a computational problem, such as when you're using
your eyes to follow a moving object. If you're always 200 ms late in
reacting you won't be able to do it, so the brain employs predictive
algorithms in these situations to compensate for its own processing
delays.

Mark

Ar Luan 29 Iúil 2024 ag 08:51, scríobh Robert O'Brien via Tweeters <
tweeters at u.washington.edu>:


> Thanks to Mark for that fascinating explanation of head (non) motion.  I

> have another question for him that may OR MAY NOT be apropos.

> In recent years there have been discussions about how flocks of various

> birds (starlings, sandpipers, etc.)  manage their motions in formation.

> I recall one study a few years back that determined that Starlings manage

> to do their maneuvers so that each one was surrounded by 6 other Starlings.

> I'm a chemist so I recognize that 'structure' as hexagonal close-packing.

> That is, if you have objects (marbles, golf balls, molecules, etc) all

> the same size then they have

> the highest density if each object is surrounded by 6 others.

> (This gets into crystalline structure such that all sorts of other

> structures are possible, especially if objects are of different sizes.

> Sodium chloride (table salt) has a cubic structure due to the difference in

> size between the small positive Sodium (+) ion and the larger negative

> Chloride (-) ion.).  Etc.

>

> But chemistry aside, in flight all the Starlings are moving, but the 6

> birds around each (except for their joint directed motion) are basically

> stationary.  And then?   Some bird(s) change direction, which is echoed at

> a delayed time by the entire flock.   This is often stated to be a means of

> avoiding predators (hawks)  but I believe Starlings do that even when no

> predators are present.  Maybe just for fun?.  (Turkey Vultures seem to sail

> around for extended periods, no synchrony, just for fun).

>

> Any comments on this Mark?  Thanks

>

> Bob OBrien   Portland

>

> P.S.   I won't bother to dig out photos, but I have noticed that

> Sanderlings running on the beach back and forth with the waves, often also

> run in formation, so that all their legs in a photograph are in sync with

> each other.    And speaking of the beach, there are fish schools that

> behave like Starlings, etc. etc.  Finis!

>

>

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