Perching

["John V Jackson" <jjackson@interalpha.co.uk>]

-----Original Message--From: Stanley Friesen Date: 19 April 1998 08:16

>At 01:22 AM 4/16/98 EDT, Dinogeorge wrote:
>>... Also, the position of the hallux
>>in cursorial, flightless dromaeosaurids does not necessarily
>>reflect its position in arboreal, probably ornithopting and
>>perching (a la _Rahonavis_) dromaeosaurid ancestors. ...
>
>I tend to think that perching per se is a rather late adaptation, only
>arrived at *after* flight had developed.  Most scansorial and arboreal
>animals I know of do NOT perch.  Even the "erect" posture so well known in
>squirrels is not really perching, as it is mostly engaged in on branches
>large enough to stand on in the normal way.
>
>I suspect that perching evolved in a volant form for one or both of two
>purposes:
> - prominent territorial display from an exposed spot,
> - ambush hunting (as in flycatchers and kingfishers).


You chaps don't seem to mention the business of clinging to palm-tree-like
trunks much.  Do you think this has a bearing?  Maybe the ability to cling
to both a vertical large diameter trunk and a more horizontal small twig is
a very specialised late adaptation - even now, many birds would find the
former difficult, whereas Archy could hardly be better suited to it.



JJ



Paul WIllis wrote 20th Apr 98:


> but it is difficult demonstrating reproductive isolation in extinct
oganisms. <

I thought that had been the definition but even biologists often seem to
ignore it for extants.

>> . . .Weishampel et al.'s The
>Dinosauria does not even cite Greg's book.<<

> I'm prepared to be corrected here but I don't think that Paul's book was
peer reviewed. This would explain why it has been omitted from Weishample
et al.. <

I'm not saying anything!