Dr Will Peach
speaker
15 appearances
1 recordings
1 series
first heard Sep 2010
last heard Sep 2010
Dr Will Peach’s voice in public audio — every appearance, attributed to the second.
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Appearances
Cats in the UK almost certainly are taking large numbers of birds and mammals.
Those numbers are not necessarily large enough to have an impact on the population dynamics of the birds themselves.
There are vast numbers of birds out there which will die naturally of starvation or cold or whatever.
And it may be that they meet their fate slightly earlier in the jaws of a moggy rather than starving midwinter.
So the fact that large numbers are being taken doesn't necessarily mean we would expect to see an impact on population level.
Clearly, predation by cats has been one of the many theories that have been proposed to explain the house sparrow decline.
And just to illustrate that, you know, we reckon there are about six million pairs of house sparrows in the UK currently, and each of those will produce on average about five fledged young each summer.
So that's giving us approximately 30 million fledged young.
Now, maybe there are 10 million cats in the UK.
Now, even if every cat takes one or two sparrows, I mean, the estimates vary, but
the average is about one sparrow per year across the cat studies that have been done, then that's still only one in three of the available fledglings are being taken by cats.
And for the house sparrow population to sustain itself, we actually only need probably six million of those 30 million fledglings to survive.
Where we were working in London, we actually went to quite a lot of trouble of
of measuring cat densities across these 70-odd sparrow colonies.
And what I can tell you now, after five years of studying those colonies, is there was no suggestion that the birds were breeding less well or the adult populations were doing less well in areas of high cat density compared to low cat density.
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