[Tweeters] Motion in Birds

[Dennis Paulson via Tweeters]

Bob, videos taken years ago of dense flocks of shorebirds (perhaps Dunlins) showed that one or more birds at the leading edge of the flock start to turn, and their turning ripples immediately through the whole flock, causing them to turn in synchrony. I can’t recall the published reference, as it is from several decades ago. Not about head movements or surrounding numbers but nonetheless just as fantastic.

Dennis Paulson
Seattle


> On Jul 29, 2024, at 8:50 AM, Robert O'Brien via Tweeters <tweeters at u.washington.edu> wrote:

> 

> 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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