Nature Notes – October 2017

As I write, there are still a few Swallows over the fields here. Most of our Swallows and House Martins have already gone, but these would seem to be late young – not unusual as the birds try to fit in an extra brood. They show up as young as they lack the tail streamers of the adults, and so look more like House Martins, but without the Martins’ white rump.

The biggest change in our countryside at the moment is the increasing development of the autumn colours in our trees and hedges. In Biology at school we learnt about the way that the green chlorophyll in the leaves is broken down, and all the useful substances absorbed back into the plant. The waste substances that remain are what give the leaves their autumn tints – a whole range of yellow, gold, red or even purple. An early favourite of mine is the Field Maple, a relative of the Sycamore and our only native Maple species. Usually kept trimmed as a hedgerow shrub, if left it will grow into a medium sized tree, with leaves and the double winged seeds rather like a small Sycamore. It is very common in the older hedges of our district, and by October its bright, pale gold leaves stand out from all the other shrubs.

We see brown leaves for a different reason, and much earlier, in the leaves of the Horse Chestnut, much loved for its conkers. By now, many Horse Chestnut trees are already very brown and dead looking. This is the work of insects, the caterpillars of a tiny moth which behave as leaf miners. They eat their way through the leaf, between the upper and lower layers, leaving large blotches which at first are merely translucent but soon turn brown. The caterpillars pupate and remain in the fallen leaf until the spring, when the adult moths emerge. There must be thousands of them, although I confess I have never seen them. Despite their narrow bodies and very small size (they are about 5mm, less than ¼ inch long), they look quite striking, shiny orange-brown with four clear white stripes. Despite all this depredation and early death of leaves, the trees do not appear to suffer in the long term, and produce leaves as normal next spring.

Wasps seem not to have been much in evidence this autumn, perhaps as a result of the weather. They are feeding on sugary foods, especially fallen fruit and nectar from flowers. In contrast, they have been feeding the larvae in the nest on chewed up meat, such as carrion and insects. Now the rearing of young workers is almost over. As well as these, the autumn colony produces young queens, and males (in Honeybees known as Drones) which will fertilise these queens. They, like the workers (but unlike the worker Honeybees which winter on stored honey) will then all die. Only the new queens will survive, to hibernate and set up a new colony next year. Watch out for these large wasps feeding on Ivy or other very late flowers, or coming into the house in search of a good spot to spend the winter!

                                                                                                              Geoffrey Abbott