Re: Waiting for a giant bird and dino physiology revisted

["David Marjanovic" <david.marjanovic@gmx.at>]

> Interesting to think of how that works for moa.  This eagle must depend
> upon finding the moa in relatively open country.  And, juveniles below
> some size would be immune from predation, I would think.

According to Maori legends, the eagle (*Harpagornis moorei*) tried to switch
from moa to humans...
this turned out to be too dangerous. (For the eagle, I mean.)
Madagascar had *Stephanoaeetus mahery*, which may be the origin of the
elephant-carrying "rock" or "ruch" of Arabian tales.

> Where
> terrestrial predation is significant (i.e., by mammals and reptiles),
> these reproductive safe harbors would not exist.  In such a
> situation--for a layer of eggs who cannot move them from place to place
> but must leave them prone for months--

Ostriches sit on their eggs. The (brown) female during the day, the (black)
male at night. Besides, they lay lots of eggs, apparently more than they can
brood.

> I would
> argue that [...] selection _for_ large size, and selection _against_ large
size is at
> equilibrium in the ostrich: further increase in size would
> both slow it down and increase its visibility at the nest; [...]

An increase in size would not slow it down if the limb muscles would grow
proportionately. There is a whole chapter in PDW that makes good arguments
that size alone is no argument that big theropods were slow.