"Nick Maclaren" wrote in message
...

In article ,
"BAC" writes:
|
| | But that doesn't seem to agree with Nick's suggestion that an
| | increase in population would lead to an increase in mortality
| | and a reduction in life expectancy which would bring the
| | population back down again.
|
| Ogilvie has misquoted again, too. Me, certainly, and probably
Murton.
|
| You mean Dr O appears to have misunderstood what you wrote?

I would assume that for most people, but his record is such as to make
that the less likely scenario. I have included the quote, in full, and
you should note the absence of any separation between what I said and
what I didn't say.

| I never said or implied that a reduction in their life expectancy
would
| result in a reduction in their population. Assuming that the latter
| follows automatically from the former shows a severe misunderstanding
| of population dynamics. Few ecologists will make that mistake.
|
| Not without precisely defining all the other variables, certainly.

Which is why I doubt that Murton said it. I got caught before by Dr O
misquoting Stace, and maligned Stace by assuming that Dr O's quote was
correct. I am trying to avoid falling into that trap again.

I have not read Murton on wood pigeons, and cannot comment on what he wrote
on the subject, and i think I'd better stop there because I've no wish to
become embroiled in a 'who said what' dispute between Malcolm and yourself.


In any case, it is notoriously difficult to estimate the effect of
changes in life expectancy in nature, as improved conditions can
equally well increase that or increase the breeding rate (with a possible
reduction in life expectancy). Almost all ecologists know that!

| Not enough grey squirrels in those wood pigeon's woods, then :-)

Well, maybe :-)

As appropriate predators for wood pigeons, I wouldn't rate grey squirrels
very highly; they aren't exactly specific! One of the reasons that I
made that remark is that I have read (informed) speculations that the
rise in the numbers of wood pigeons and collared doves may be a factor
in the near-demise of sparrows. There is certainly a fair correlation,
and a realistic causal chain. And, if so, grey squirrels clearly aren't
any use at controlling pigeons, as they are at population limits in the
most sparrowless areas.


The grey squirrel reference was a joke, of course.

The increase in collared dove population is an interesting point, because
they are relative newcomers, and there does seem to be a correlation between
their establishment here and the sparrow decline, although that may merely
be coincidence. What is the 'realistic causal chain' you have in mind,
though?