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Re: Perching, climbing, roosting was Re: 11th specimen of Archaeopteryx



Anthony Docimo <keenir@hotmail.com> wrote:


> There was a statement earlier in this thread...something along the lines of 
> "yes, and those are all descended from perching birds."


Yes I'm aware of that - and it's a good point.  However, I was using
the example of the turkey to demonstrate that a hallux that is
large/low enough to grip branches does not interfere with the ability
to forage on the ground.  I was refuting the argument that having a
terrestrial pes is somehow a deterrent against evolving a pes that can
also grip branches.


>> I'm afraid I don't understand the relevance of the flamingo. AFAIK,
>> it doesn't perch or roost in trees. It spends its days (and nights)
>> on terra firma.
>
>  I think his point was a rebuttal of the claim that a bird's (or protobird's) 
> feet are shaped by where it sleeps.


Yes, but... if you are a theropod that walks on the ground, no extra
pedal adaptations would be required to stand still on the ground,
including when sleeping.  However, if a theropod were to roost in the
crowns of trees, I'd be surprised if it could "get by" with simply
co-opting its terrestrial adaptations into an arboreal setting.  If
the animal walks on the ground, and sleep in trees, then the latter
should foster some changes in pedal morphology.  Simply having claws
isn't enough.


>  By that logic, there shouldn't be anything (that hops or flies) living in 
> deserts - that substrate actually moves.


Yeah, but if you fall over in the desert, the fall typically won't
kill or maim you.  If you fall off a tree branch, it might be a long
way down.  As the saying goes, it's not the fall that kills you, but
when you hit the ground.


> Heck, there shouldn't be rock wallabies  (gravity + uneven rocks + some rocks 
> come loose)  or thorny forest lemurs  (gravity + thorn-
> covered branches)


These animals have specific adaptations to these lifestyles.  Your
statement underscores my point.


>> Briefly, climbing up trunks and foraging within the crown promotes
>> different adaptations.
>
> you have to get to the crown in order to feed in it.


Birds fly up into the crown to feed in it.  Certain birds climb trunks
because they obtain food from the trunk, like woodpeckers,
treecreepers, and nuthatches.  The feet of these birds have special
adaptations for trunk-climbing (and trunk-clinging).






Cheers

Tim