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Re: Harmonious depredations
The point that you have not admitted is that ostrich nesting is dependent
on predator presence. Until you do so, you are saying that they have
nothing to fear from predators. My argument depends on this
Nonsense. Ostrich nesting is dependent on maximizing the production of
young ostriches. As for predation, of course nesting behaviour can be
influenced in an evolutionary sense by predator pressure (and while we're
at it let's distinguish between egg predation and predation on brooding
adults). That doesn't make predation the only selective factor involved.
Your argument is not that reproductive behaviour is influenced by
predation. Everyone admits that. Your argument is that egg predation
exterminated the dinosaurs, and as far as the ostrich is concerned you are
trying to avoid the evidence that ostriches tolerate continental predation
levels. As such, it is you who are arguing that ostriches have nothing to
fear from predators because their current nesting behaviour is so cryptic
that predators cannot locate their nests, and that therefore their survival
does not affect your position that dinosaurs, which (you claim) did not or
could not exhibit such behaviour, must have been exterminated by such
> authoritative Handbook of the Birds of the World, with the caption "...the
Are you suggesting that this entry should trump Bertram's study in some
way? He clearly indicates that if ostriches nest in places easily
accessible to hyenas that all nests will be taken.
Bertram's study, however valid, was not (I believe) meant to apply to every
ostrich population wherever it occurs (and historically that was from the
Arabian deserts to the Cape). I have already stated that predation is very
high - but the point is, it does not exterminate ostriches asnd did not
stop them from evolving (probably in Asia) in the first place.
> Though rheas frequently hide their nests, "the male sometimes uproots all
> the vegetation within a radius of 2-3 meters around the nest,
> isolate it, in case there is a fire".
The fact that rheas will on some occasions not only not try to hide their
nests in vegetation but will actually remove what might have been
protecting vegetation to create a bare patch up to six meters across
centering on the nest hardly suggests that they rely on crypticity to avoid
> Emu nests are "always in a fairly
> open site, where the sitting male has a good view of the surrounding land".
"Open site" lacks definition. Open site with grass? On sand dunes? I'm
not being critical of HBW, only stating what we say to all our
students: you must go deeper than encyclopedias.
I am restricted by the material to hand in my home library. However, I
spent two years doing field work in Australia and can certainly testify
that emus are often found in areas where there is little or no tall
grass. Also the HBW is far more than an "Encyclopedia", and I have not
seen you provide any citations whatever on emu nest site preference.
Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2 mailto:firstname.lastname@example.org