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Re: [dinosaur] Energetic cost of foraging flight in parrots



Dann Pigdon <dannj@alphalink.com.au> wrote:

> One thing I notice about the species of bird used in the study is that they 
> have
> unusually short tail feathers, which would seem to be an adaptation to leaping
> about in closely-spaced branches. Most early theropod flutterers appear to 
> have
> had long bony tails that would have made navigating such a cluttered 
> environment
> quite difficult, especially if the feathered tail 'frond' lacked the mobility 
> of modern
> bird tail feathers and couldn't be spread or retracted at will.


This illustrates one of the pitfalls of using extant birds as analogs
for proposed incipient flight behaviors (e.g., in early avians and
their relatives).  Although early birds and certain of their non-avian
relatives have relatively large wings, their morphologies were
otherwise very 'primitive' (plesiomorphic): pectoral girdle, tail,
foot.  Arboreal foraging doesn't 'fit' the morphology of
archaeopterygids and microraptorines. The same issue also comes up
with WAIR.  (I also think it's highly inaccurate that the juvenile
hoatzin is cited as an analog for alleged tree-climbing behavior in
archaeopterygids and other early birds... but that's a whole other
topic.)

I don't wish to be hypercritical of this arboreal foraging study; when
it comes to the behavior of this parrot species, and the success of
arboreal foraging birds in general, it's extremely interesting.  But
IMHO the extrapolation of perch-to-perch foraging in parrotlets to
basal paravians like archaeopteygids and microraptorines is highly
dubious.  Arboreal foraging might have been important in the
refinement of the avian flight apparatus (in basal ornithothoracines,
and possibly sapeornithids and confuciusornithids), but it's unlikely
to have been a factor in the evolution of aerodynamic locomotion in
the earliest theropod flutterers and fliers.  In short, I doubt it was
a 'pre-flight' behavior.