In article ,
"BAC" writes:
|
| [ Quoting the RSPB ]
|
| The study found that songbird numbers were no different in places where
| there were many magpies or sparrowhawks from where there are few. It found
| no evidence that increased numbers of magpies have caused declines in
| songbirds and confirms that populations of prey species are not determined
| by the numbers of their predators.

The last clause is plain and simple drivel. There are many circumstances
under which the populations of prey species ARE determined by the numbers
of their predators. If we assume the previous statements, what it really
shows is that, in THIS case, IF there is a SINGLE cause, this is not it.
In turn, that makes it unlikely that this is a major factor.

Whether or not this a factor at all cannot be determined from such a
simplistic analysis. Indeed, it is equally possible that magpie and
raptor predation actually increases songbird numbers as reduces them;
there are several known mechanisms for that effect!


Regards,
Nick Maclaren.