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Ratites and egg predation: the pattern confirmed.
According to this text book, where there are indigenous mammals there is one
large flightless ground-laying bird in all of Africa, one in the American
Continent, and two in Australia. I won't count all the stealthy egg
layers, just the ratite's caranate relatives. There are 8600 extant birds. In
birds that gives us a non-stealthy to stealthy egg-layer ratio of
This number is the ratio for species. Do the same thing for abundance
and the number is vanishingly small!
I don't believe ratites can be used as an example of the viability of
the large, non-flying, egg-laying life-style. Yes, it is an exception
to my "all non-stealthy egg layers became extinct" rule, but I hope
you'll agree that it is easier to explain away each of these in terms
of reproductive strategies etc., than to explain the specificity of a
bolide's effect on such a diverse and robust group as the dinosaurs.
I know only that ostriches have some bizarre behaviours such as all
the hatchling going with one mother (to enhance chances of avoiding a
randomly searching predator. They do this at the margin of a desert,
I think (fewer predators). Perhaps (speculation) this was a place
which dinosaurs, mammals and birds didn't go to as much. I really
don't know. But I know that ostriches have a terrible time getting
by. They have many clutch failures--I don't know if they suffer egg
predation or not.
Look, the scarcity of ratites vs. stealthy egg layers is so stark, this
has to tell you something about the effectiveness of the comparitive
reproductive strategies. Stealthy egg-layers win, 8600 to 4.