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> Ah, but there is. The evidence is that, where predators are scarce, birds
> frequently evolve "back" into flightless forms.

     Not knowing much about Cenozoic bird eveoluton, are you saying that 
the first flightless (were they always flightless?) ratites evolved in a 
predator free environment?  I understand there is a current theory that 
ratites are a monophyletic group descended from a single flightless 
ancestor widely distributed across Gondwana during the early Paleocene, 
In which case they must have been living around predators.  What about 
Diatryma or the Phorusrhacids?  I realize all these birds 
(except for the isolated kiwi) are humungous birds, some of which were 
predatory themselves, but is there any evidence that thier ancestors were 
small, flightless, and evolved in environs where they may have been 
subject to predation?

LN Jeff