Jim C wrote: >underwater 'flying' requires substantially more pronation during the downstroke
than flight in air< I would qualify Jim's statement with the observation that not all swimming by birds is underwater swimming. Several years ago I saw an eagle kill a seagull on a Maine lake and watched as it hauled the prey to shore by swimming at least 100 yards with the prey in its talons. When swimming, the eagle used its wings in an almost identical stroke pattern as would a human swimmer doing the sidestroke, keeping its head above water at all times. The eagle was not simply thrashing about--it was a very systematic and efficient swimmer and swam in a straight line to the nearest point of land. I'm just offering this as an observation---I don't believe the avian flight stroke evolved in response to selection for swimming of any sort. PTN ----- Original Message ----- From: James R. Cunningham Sent: Thursday, April 11, 2002 1:37 PM To: TiJaWi@agron.iastate.edu; dinosaur@usc.edu Subject: Re: Cost in Aquatic Birds (long) I'm curious and have a question about the old thread that postulated flight
origins in the water (I don't know if that was the progenitor of this thread,
but it was convenient to post by hitting the reply button on this message).
Sorry if I'm off-thread. For those who postulated that archie was an aquatic
swimmer, have you considered the following? For reasonable thrust efficiency,
underwater 'flying' requires substantially more pronation during the downstroke
than flight in air (because the body weight doesn't have to be supported in the
water). If archie were a swimmer, there should probably have been substantial
adaptations for increased pronation-supination ability at the shoulder, to the
extent that it should be observable in the fossil record. This should require
either an advanced supra-coracoideus (sp?) or an equivalent mechanism. I know
the s-c isn't advanced. Are the equivalent modifications present? If not, it
might imply that archie wasn't much of a swimmer, if at all.
All the best,
JimC
Williams, Tim wrote: snipped
> Jaime Headden wrote: snipped
>
|