More on Sparrowhawks

I was told this morning of a kingfisher kill locally, almost certainly by a sparrowhawk, which is to my mind remarkable and can't happen often, both birds being such able and agile fliers. I've also had a number of conversations with people who are very negative towards sparrowhawks, which I am tempted towards when I think of the kingfisher, but  am not in general.

Are there more sparrowhawks? Yes, they've certainly increased over recent years. Do they kill garden birds? Yes, of course, and feeding stations provide a better opportunity than the hawk will find in most other locations. Birds are gathering there in good numbers and very regularly, and sometimes the placing of feeders allows plenty of cover and opportunity for surprise. We've tried to ensure that's not the case in our garden, but it's quite a small patch. But, third question - is that a problem? No, I feel.

We are maintaining an artificially high population of many garden species due to regular feeding, and therefore we're bound to boost the population of sparrowhawks. However, this is a classic case where predator and prey species are kept pretty much in balance, with the numbers of sparrowhawks fluctuating in a way that matches the charts for prey species, with the curve on the predator graph a little behind that of the prey species. If sparrowhawks kill too many prey species, then prey becomes rarer, and there is a consequent decline in sparrowhawk numbers.

The same principle of balance does not apply, though, to certain other species, with magpies being one I'd particularly note. I like magpies, and they regularly visit our garden without doing too much harm. They do, however, predate on small birds, and in particular they take eggs and nestlings. If the garden population of small birds is artificially high (which it is), many nests may be built in not very suitable locations (that will also be the case if gardens are too tidy and bushes and hedges too well-trimmed). If the gardener can see the nest, so can the magpie, or, for that matter, next door's cat.

I think that a major factor in maintaining a higher-than-it-should-be population of magpies is roadkill. Crows in general cash in on roadkill, but I rarely see a dead creature on the road without magpies around. This must have a seriously beneficial impact on magpie numbers, and means that those numbers are not closely correlated with those of small garden birds in the way that sparrowhawk statistics are.