Re: bird heads

["James R. Cunningham" <jrccea@bellsouth.net>]

Betty Cunningham wrote:

> I'm contending that 'bobbing'/adjusting the head (specifically) for
> visual acuity (new halloween party game?) was greatly reduced or
> eliminated during flight.

> The bird 'bobs' it's head as a means of adjusting for this bounce to
> it's vision.  I'm suggesting that during flight this gravity-induced
> repeating vertical shock is reduced.  Wind and air pressure replace
> gravity-induced vertical pressure as the biggest shocks to the system.

With the exception of severe gusts, or other occasional sources of wind
shear (updrafts, downdrafts, etc.), I suspect that the cyclic inertial loads
(including 'added mass' effects) due to wing flapping will be the greatest
source of 'bobbing' during active flight (as opposed to soaring).

> The bird is basically suspended in the air like a plumb bob is. Thus no
> need to physically 'bob'/adjust the head to match body system shocks-the
> system has to adjust as a whole unit as the wind/air pressure hits the
> whole bird.

Inertial loads caused by flapping affect the wing differently from the body
and from the neck and head.  Among other things, there's a phase lag.
However, in pointing this out, I am not drawing or suggesting any
conclusions with reference to your discussion.

Jim