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Re: Great in the air, not so good underwater
So, for example, large seabirds are loading limited to the extent
that they have to be able to hit steady state from a running start
and they can only run so fast.
No, they don't have to be able to hit steady state directly from a
running start. All they have to hit is an anaerobic burst window, and
have the ability to accelerate to steady state before the burst power
Point taken. Just the same, the running launch system has particular
constraints and benefits. I should have said "to reach their burst
window" rather than "to hit steady state".
And swans use a very different technique that involves (in visual
extreme -- for purposes of qualitative illustration) a
'hovercrafting' technque combined with 'jet thrust augmentation'
during a portion of the flapping cycle...
Yeah, swan takeoffs just blow my mind. Cool stuff. I was mostly
referring to sulids and procellariiforms
when I mentioned running starts in seabirds before. I probably should
have been more specific. Grebes and loons also use running starts, but
those are different, as well.
However, my real point is that if flight is truly important to the
animal, it or its decendants will partially sidestep the launch issue.
A couple of ways to accomplish this are cliff launching and front
limb assist during launching (I'm not sure how a bird would accomplish
that latter, but bats and pterosaurs can). Given enough time for
evolution to operate, I suspect there are hundreds of other ways as
I'm sure there are very many indeed. What launch modes are open seems
to basically depend on the old standbys of historical constraint and
selection. Constraint pretty clearly prohibits the forelimb-assisted
launch cycle in birds, and thus I doubt they'll ever produce volant
members as large as pterosaurs. Stabilizing selection is probably hard
at work, too, though: despite denying some helpful launch modes, avian
bipedality has some great advantages. In fact, being bipedal gives
birds access to some launch solutions denied to pterosaurs and bats;
the ones I have in mind work best at small to medium body sizes.
Still, I'll bet nothing beat seeing a Quetzalcoatlus catapault off the
ground...makes me sad that they're gone.