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Ronald Orenstein wrote:
> This is just a guess, but I wonder if it might have something to do with
> the development of the ramphotheca, the horny sheath that covers the bills
> of modern birds. Possibly the migration of the nostrils to near the base
> of the sheath in some way strengthens the thing structurally, or possibly
> makes it less likely that the nostrils will get clogged or injured as the
> bird uses its beak for pecking or probing.
> Note, however, that kiwis have their nostrils near the tip of the bill, not
> at its base, presumably because smell is important for them in locating
> food. This is, I would expect, a secondarily derived placement.
> Ronald I. Orenstein Phone: (905) 820-7886
> International Wildlife Coalition Fax/Modem: (905) 569-0116
> 1825 Shady Creek Court
> Mississauga, Ontario, Canada L5L 3W2 mailto:firstname.lastname@example.org
Yes, it could be aerodynamics at work. Or perhaps the function of a beak
concentrates its usefullness towards the tip, in which case the
front parts of the beak may have elongated and the rear sections
been reduced. It may also be similar to the position of sauropod
nostrils. Presumably sauropod nostrils moved higher up to protect them
from sharp conifer needles or araucarian leaves when the mouth is
thrust among them. Birds, having no real means to grasp with their
highly specialized forelimbs (hoatzin excepted), tend to do everything
with their beaks, so perhaps the nostrils have been relocated to a
less active area of the beak for protection, to allow beaks to be
thrust into tree hollows, used for defence, or whatever.
However the kiwi presumably does these things too, and since it
is quite flightless (you couldn't get a less aerodynamically designed
bird) then perhaps aerodynamics are a better explanation after all.