G'Day Mates
Thanks for the reply mate.I feel more educated now.Is
that 100% mortality or what............? If you havnt
seen many dead birds lately stand near a canon net
when its fired over a flock of waders or go on a ozy
bbq with Dr Day. You Oz crickers always got the
answers. Wityh your freakin flippers.
D"Day Mates )of to trainin(
I don't see that many dead birds around,
> thus I stand by my statement that much mortality is
> unseen.
>
> Do you get my drift/swing or have you caught a
> flipper?
>
--- Peter Woodall <> wrote:
> At 11:36 8/02/2001 +0000, you wrote:
> >G'Day Mates
> >
> >I am a pommy cricket supporter and have been
> watching
> >your debate about canon netting. Now i am not an
> >educated man but had to laugh when Dr Woodall wrote
> >the message below when discusuusing the mortality
> >caused by cannon netting. Now i bet the lot of you
> >that over a 100 years the mortality rate for wild
> >birds is about the same as humans. I see you have
> a
> >namesake of mine (close) on the list.
> >
> >G'Day Mates
> >
> >Shane
> >
>
> Dear Shane,
>
> I think you'd best stick to watching cricket.
>
> Let me explain.
> If we assume that the population is stable, not
> increasing nor decreasing,
> and there is no net immigration or emigration, then
>
> births = deaths.
>
> For a pair of humans (in the west) over their
> lifetime (65 years):
> births = just over 2
> deaths = just over 2 (the parents, and a small
> proportion of their children)
> mortality rate 2/65 = 0.03 per year per pair
> [even in the Third World the figures would be
> something like 10 births, 10
> deaths]
>
> .... and the population remains stable.
>
> For a pair of birds, say Pacific Black Ducks with a
> lifespan of say 2 years
> on average,
> although some live to 10 years in the wild (from
> banding studies):
> births = average clutch of 9 (range 7-13) (I'm
> only allowing for one breeding
> season but there could be more);
> deaths = about 9 (the two adults and 7 of the
> offspring, leaving two to
> maintain the population).
> mortality rate = 9/2 = 4.5 per year per pair
>
> Small passerines (song-birds) in the northern
> hemisphere have similarly
> large clutches, short lifespans and high mortality.
> Small birds in the
> southern hemisphere tend to have smaller clutches,
> but live and breed much
> longer,
> and have a lower mortality
>
> So, over a lifetime, birds have much higher
> productivity than humans,
> and thus much higher mortality. The annual
> mortality
> the difference is even more striking.
>
> Over the 100 year period you mention,
> there would be about 3 deaths among the pair of
> humans and their offspring;
> there would be about 450 deaths among the pair of
> ducks and their offspring.
>
>
> I don't see that many dead birds around,
> thus I stand by my statement that much mortality is
> unseen.
>
> Do you get my drift/swing or have you caught a
> flipper?
>
> Cheers
>
> Pete
> Dr Peter Woodall email =
>
> Division of Vet Pathology & Anatomy
> School of Veterinary Science. Phone = +61 7 3365
> 2300
> The University of Queensland Fax = +61 7
> 3365 1355
> Brisbane, Qld, Australia 4072 WWW =
> http://www.uq.edu.au/~anpwooda
> "hamba phezulu" (= "go higher" in isiZulu)
>
>
>
>
>
>
>
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