[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re:Fw: avian flight



<<> Big flightless birds evolved in australiaand other isolated(big or small)
> enviroments because of the absence of big
> predators..you know how the story ended.

Hah! Big flightless birds evolved in Australia: Dromornithidae have just
turned out to be carnivores!
Big flightless birds evolved in Laurasia: Gastornithidae ("Diatrymidae")
have been confirmed to be carnivores!
And phorusracids...
All these were the big predators themselves!>>
 
so...?
I said that they evolved because there were non big predators(this is  probaly not true, but it's not important for what i'm saying), not they couldn't have become the ruling predators themselves..
 
 
Were the flightless birds that evolved in areas where big mammalian predators were present, all carnivorous?
what about non-carnivorous(whatever this means in the single cases) flightless birds having evolved in hunter-poor areas  and carnivorous birds in more competitive ones(from the point of view of predation)???(I'm not proposing this, I'd only like to know if its true or not, since I think it's already known)
 
<<Carnivorous mammals were around in all these areas all the time. They just
didn't grow larger>>
 Do you consider it(or anybody else with more knowledge than me) as being the consequence of the presence( competition by) of big predatory birds or the same reason for which these birds could evolve?..i think it would be hardly possible to know, but i ask....
 
<<I don't know much myself. I just can tell that for much of the Neogene
ostriches were present in all European and Asian steppes>>
Ok, thanks for the info, but I'd rather focus on their origin more than their presence in some zones.
..However the fact that their remains come from deposits covering a long period of time, likely means that they got exitint after a long permanence( and perhaps not even because of predatory pressure) in these areas, so their success could  have been less related to the absence of mammalian predators than suggested....