"michael adams" wrote in message
...

"BAC" wrote in message
...

"Nick Maclaren" wrote in message
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In article ,
Malcolm writes:
|
| If the birds weren't shot, the mortality would go down and their
| life-expectancy up.

That is extremely unclear, and might be the converse of the truth. It
will depend very much on how close they are to overpopulation at the
stressful times of year.

It is quite possible that stopping shooting them would cause an
increase
in their population, and a consequent increase in their mortality rate
and a reduction in their life expectancy. That is what often happens
to prey species with effectively no predation - as is the case for
wood pigeons in many parts of the UK.


Are you saying that, for a given ecosystem, only a certain maximum number
of
a population of birds can be expected to survive the winter, regardless
of
how many more than that number started the winter?


All other things being equal any given ecosysyem can only produce
a limited amount of food which can only support a limited number of
birds.

Given the rate at which birds such as wood pidgeons can reproduce
its fairy clear that all other things being equal they will exhaust
the food resources of any given ecosystem within a few generations.
With surplus birds either moving elsewhere - which doesn't really
soleve anything, or simply dying from starvation. Thus maintaining
an equilibrium.

We have been plagued with Parakets (SP?) for many years, some idiot, years
ago decided he could no longer cope with them, so released them into the
wild, and they bred as though there was no tomorrow, the noise they made was
almost as loud as the aircraft which pass over from Heathrow.

I haven't seen one this year at all, what could have happened to them, there
were literaly hundreds of the things.

Alan