Re: Perching

[Stanley Friesen <sarima@ix.netcom.com>]

At 03:15 PM 4/20/98 +0100, John V Jackson wrote:
>-----Original Message--From: Stanley Friesen Date: 19 April 1998 08:16
>
>>I tend to think that perching per se is a rather late adaptation
>>...
>>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?

Well, I wouldn't limit it to palm-like trunks.  What I see in the smaller
members of the basal coelurosaurs are animals adapted as scansorial - mixed
arboreal and cursorial.  Such animals climb straight up all sorts of trunks
as easily as they run along the ground.  The most familiar living
scansorial animals are the squirrels.  These are also quite agile on
"major" horizontal branches.

>  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,

Actually, I would consider that a *loss* - due to the loss of claws on the
hands (presumably for aerodynamic efficiency).

> whereas Archy could hardly be better suited to it.

Quite so.

On the other hand, at least some researchers have claimed that Archy's feet
are *not* well suited to perching - due to a difference in the curvature.
(The opposite has also been claimed, and I am not quite clear enough on the
arguments to adequately judge who is right here).

--------------
May the peace of God be with you.         sarima@ix.netcom.com
                                          sfriesen@netlock.com