1). What you say about the ptero launch technique seems to make sense if the image I have taken from context is correct. I am sure that I am behind on my reading. Do you have a reference that delineates this launch cycle in detail? That would help a lot. --Don
No, herons are nowhere near any limit. Yet they use most of their potential stroke amplitude till they get going. --Don
My take is most easily expressed by re-stating two of
your sentences. Quantifying launch abilities _from a skeleton(s)_ is a
mechanical problem. The _probability_ of achieving the phenotype for a
given launch technique through natural selection is critically affected by the
"ecological part". Were mega-volants the only phenomena difficult to explain relative to current conditions I would be much less hard-headed (by the way). --Don
2) I agree entirely that limits vary per flightstyle, but there are absolute limits, per medium. It is not possible to infinitely improve locomotive phenotype. Further, I posit that, because any living system must engage in multiple processes, theoretical limits for a given process can be approached (rarely), but not achieved. --Don
High altitude migratory birds aren't optimized for sealevel flight, even if they nest there, as high altitude selection obviously occurs. Those examples demonstrate very little about density effects. (Heh. Wind blows like hell up there. V^2 and all that.) --Don
At _any_ weight, the effects of medium density change are NOT easily compensated for if the other critical variables (circulation, temperature, and composition) are controlled. The effects are easily observable in lab in both wing kinematics and various metrics of power, especially lift generated per power expended. --Don
Further, the flight morphologies of birds that are optimized at
5500' are measurably different relative to sealevel birds (per flightstyle/species), ditto w/ insects. (See Feinsinger P, Am Nat v 113, #4, 481-497 for Andean hummingbirds). --Don
3). I see the relevance. The point is that there is not an observed change i
g birds across very different atmospheric densities. You suggested previously that a 15% atmospheric difference would be significant for large vertebrate flyers... --MH
3). I don't. This conversation started out w/ mega-volants. Now, you seem to be saying that because a 27 lb goose can fly in uncontrolled conditions, that is support for a 150 lb whatever flying in standard air. I am surprised you put forward these 'in vivo' anecdotes. --Don
I haven't read any author that feels that the extant maximals show any potential for doing well or better (as you seem to imply) at larger sizes. I grant you, they continue to be volant, but just barely (in still air). --Don
Also: Reference on Quetz. performance, please. (Heh. You sound like you got one in the backyard. Kin I see him? }: D.) --Don
As to size limits, please allow me to communicate by re-statement again. I think of the mega-volants as _approaching the practical size limits for their flight morphology at that time_. And I feel you should say, "_theoretical_ mechanical size limits" no matter how much modeling you've done. --Don
4). I like "maximal volants". Actually, "... the largest observed volant species of their time intervals..." is an excellent definition of what maximal volant refers to. --Don
Plot wingspan vs time,
are the minimums... it is a math thing, as you know. As the specimens are obviously "observed", the burden of distinction falls on those who use the term "maximal" in the theoretical sense. In the same vein, the declining trend of maximal wingspan exists, and as such is real, unless new data destroys it. Relevance or statistical significance may not exist, but I don't think the term "real" should be used as a substitute for "relevance" or "significant". It may sound cool, but it limits the language, and causes confusion. --Don
Cheers,
--Mike H.