Bird attacks!

Can blue tits save our conker trees? You could help us find out. It will only take a few minutes and, with enough records, we can begin to understand how blue tits are responding to the horse-chestnut leaf miner. We launched the mission last year, but we hope to have more records this year.
We know that blue tits (along with great tits and coal tits) do feed on horse-chest leaf-miners. They peel open the leaf mine to extract the pupa inside.

You might have noticed blue tits feeding in the canopy of horse-chestnut trees, but bird-attacked leaf-mines are easy to spot and count. (Photo by Richard Broughton)

But which trees to they attack? Is it any tree, or do they preferentially attack the most infested trees and leaves?
And, does that activity occur everywhere? Or is it a behaviour that is spreading across the country (such as when blue tits learned to attack milk bottle tops to get the cream)?

The evidence of bird attacks. Look for these and count them to take part in the bird attacks mission of Conker Tree Science (you don't have to wait to watch the birds themselves).

Download the instructions, spend a few minutes counting bird attacks on horse-chestnut leaves (it's an ideal activity to do with children, but adults can do it on their own as well!) and then submit the results. With enough records we should be able to answer these questions - so by counting bird attacks you'll be contributing to real science.

The state of our conkers

Earlier in the summer I commented that the horse-chestnut trees in my area weren't too badly affected affected by the leaf-miner. What is the situation now?
Well, my impression is that the leaf-miner damage is a lot more variable than in previous years. By this time of year I would have expected almost all the horse-chestnut trees to have completely brown leaves that were curled up and dry (especially at the base of the crown of the tree). Instead some trees are badly affected (though maybe not as much as previous years?) while other trees are much more lightly affected.

A badly affected tree (complete with conkers) in my village. I think the trees were even more badly affected by the leaf miner last year. From research published last year, those conkers will be smaller than they used to be, thanks to the effect of the leaf miner.

This tree, just a couple of hundred meters up the road, is much less badly affected. Last year in was affected much more badly by the leaf mine.

I still suspect that the exceptionally late spring could have caused this effect - by affecting the first generation of the leaf-miner moth, it would have had a knock on effect on the second generation. Maybe, the very local variations in shelter and warmth of trees earlier in the spring was sufficient to cause this variation? In previous years it is possible that there were so many moths anyway, despite local variations, that they quickly reached a 'saturation point' on all trees.
That's just a theory, and the fact that every year is different is part of what makes ecological science fun. But it also makes it really difficult to make precise predictions about the future!
For now though, I'm enjoying horse-chestnut trees with some green left in their leaves - something I haven't seen in September for many years.