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Re: Subject: Bird hibernation/torpor



At 12:58 PM 3/23/97 -0500, John Bois wrote:
>But how about this:  ostriches, with their enhanced osmoregulatory
>abilities were able to range and reproduce in habitats unavailable to
>many of their predators.  This being true, desert ostriches enjoyed
>greater reproductive success than tropical rain forest ostriches.

I doubt this VERY much.  First, in Africa there are far more potential
ostrich predators outside the rainforest than in it (lions, for example, or
cheetahs, or Cape hunting dogs, or hyenas, none of which occur in
rainforest).  Second, Ostriches are not purely desert animals but occur in
savanna woodland in much of Africa.  Third, ostriches are thought (as for
many other plains animals in Africa) to have evolved in Asian steppe lands
and moved into Africa later - there never were any "tropical rainforest
ostriches" as far as we know.  Fourthly, ratites can do quite well in
rainforest, as the cassowaries show.

>     Now I have come up with a parsimonious idea which can well
>account for the "terror birds" viz.., they could hide their nests
>in the tall grasses of the savannahs. 

But this does NOT fit the nesting patterns of either ostriches or emus, so
it is only "parsimonious" if you ignore what the largest living birds are
doing.

 These hiding places were
>not available to dinosaurs because there were no grasses at the
>K/T. 

But there were cycads, ferns (ever been in a bracken thicket?) and other
plants that could easily have provided plenty of cover, were any needed.
There were lake islands.  There were forests.  Lots of places to hide
nests... And of course eggs could have been protectively coloured (as are
the eggs of birds that nest on sandy beaches today), or covered with
vegetation when not brooded, etc etc.

> I am going to argue that
>deserts were not as available to dinosaurs as they are to
>ostriches

On what basis?  And what does this have to do with savanna ostriches?

>Ostriches depend on grass and the things
>that live in it. 

The only ostrich nest I have seen, in Serengeti Park, Tanzania, was on bare
open ground.

 
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          Internet: ornstn@inforamp.net