Doubts about magpie cull
I King (Mailbox, March 14) may be distressed by magpies taking fledglings to feed their own young, but that is nature.
The real argument for culling magpies and other corvids is that it is needed to stop the current decline in song bird numbers and would be effective in doing so. I am not convinced of this.
I do not deny that, under some circumstances, predation by corvids species may have an impact on song bird populations. I did a small piece of research a few years ago, which suggested that magpie numbers do indeed impact on house sparrow numbers, but that does not mean that culling magpies is necessarily the best way of boosting sparrow populations.
Corvids and song birds had co-existed for a long time, before song bird numbers started to decline. This suggests that we need to look at what has changed, if we are to understand the decline. This means looking at things such as changing farming practices and loss of greenery and more managed gardens in urban and suburban areas.
Natural systems are complicated and if we have destabilized them through our interference then more brute force interference is not necessarily the best way to repair the damage.
Without doing something to reverse the decline in food supply and nesting sites for song birds, removing predators could just lead to more birds starving.
And culling corvids might not even be effective in reducing numbers – I know of one study that found that shooting rooks had no impact, since their population was actually controlled by the availability of food over the winter and the reduced competition for food meant that more birds survived.
Malcolm Hunter, Highfields.
4 Comments
by Sarah, south
Saturday, March 26 2011, 6:03PM
“Malcolm Hunter points out that corvids and songbirds "co-existed" for a long time before songbird populations began to decline. Might one reason be that it has long been considered acceptable to cull crows and magpies, and only recently has this been challenged? It would be interesting to compare the dates of the rise of the "pro-magpie" lobby and the beginning of the decline of songbirds.
Personally I think a more relevant comparison would be between the massive rise in the cat population over the last 30-40 years and the decline of songbirds, but that's opening a whole other can of worms...”
by Andrew, Leicester
Saturday, March 26 2011, 4:12PM
“Since "Gordon Bennet" seems to know what it is that really limits magpie populations, and has the detailed knowledge of ecological interactions which (as Malcolm Hunter points out) mean that simply killing a predator may not lead to an increase in numbers of its prey, perhaps he should let us in on the secret?”
by Gordon Bennet, Leicestershire
Saturday, March 26 2011, 2:10PM
“Watch pairs of magpies working together throughout the breeding season. One will make a lot of noise and flapping near to the nest of a songbird. The songbird responds defensively by leaving the nest to drive away the threat. While it does so, the silent one of the magpie pair slips into the nesting site and takes the eggs or young birds. Typical clever corvid behaviour! Magpies are not dependent on these easy snacks for their survival and thus their population remains stable. Songbird populations however do suffer as a result of this particular predation. With grey squirrels, cats and various human interventions they don't stand a chance.”
by Gordon Bennet, Leicestershire
Saturday, March 26 2011, 2:08PM
“Watch pairs of magpies working together throughout the breeding season. One will make a lot of noise and flapping near to the nest of a songbird. The songbird responds defensively by leaving the nest to drive away the threat. While it does so, the silent one of the magpie pair slips into the nesting site and takes the eggs or young birds. Typical clever corvid behaviour! Magpies are not dependent on these easy snacks for their survival and thus their population remains stable. Songbird populations however do suffer as a result of this particular predation. With grey squirrels, cats and various human interventions they don't stand a chance.”