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Re: Pterosaurs and birds, was Re: birds and pterosaurs



Are you thinking there is a metabolic difference
then?

Yes, but not difference in general body metabolism, but in energy and specific aminoacids dedicated to form flight feathers.


Oh, gotcha, I misunderstood before. Interesting thought. I wonder how much of a large bird's metabolic costs go to feather replacement; that would definitely be very interesting to know. Thanks for clarifying that point; I like it.

I think a paleontologist may not be accustomed to
think that physical efficency of animal is relative to
it's ecological niche.

Very large bird might be inefficent, but will evolve
and live when more efficent pterosaurs are extinct.
Their ecological niche may be restricted, but if there
are very food-rich conditions, they will evolve.

Oh, I don't disagree that pterosaurs had advantages as large-bodied flap-gliding/soaring forms, and that the appearance of soaring birds only after the K/T extinction is telling. Very large birds were probably quite efficient, but large pterosaurs were probably more efficient as soarers, with regards to energy extraction (though soaring birds may have other advantages we are missing). I was arguing more against the idea that extremely food-rich conditions are required for the evolution of giant soaring birds, in large part because large size is an advantage in searching large ranges for such animals (and thus somewhat helpful for conditions with low food density). It might be required, but it doesn't seem convincing at the moment.


Thanks for the snippet; that's very interesting.  I
wonder why the molt
is so slow in those groups...

Because soaring bird can lose only few feathers at a time. With slow speed of growth, big feather length, many feathers - the cycle of replacement becomes long.

Right, that much makes sense. I was wondering why the feather growth was so slow. But it may just be because the growth is being measured as a linear growth rate, and the feather has to scale as 3-D structure (albeit a flat one).


--Mike