There is not yet a big change to autumn colours in the woods and hedges, but it will only be a few weeks. I am particularly fond of the contrasting colours that the hedgerows show – brilliant yellow/gold in the Field Maple, and purple in the Dogwood. There is also the red of the abundant Hawthorn berries, except in those hedges which have been recently trimmed. However, there is already a change in many of our Horse Chestnut, or Conker trees, which turned a deep rusty brown as early as August. As is now widely known, this is not a natural autumn colour, but the work of an insect, the Horse Chestnut leaf miner (scientific name Cameraria ohridella since you ask). The mining is done by the caterpillars, which eat the inside of the leaf tissue between the upper and lower surfaces, leaving brown patches as those parts of the leaf die. They can be clearly seen if the leaf is examined. There may be many such galleries on each leaf, so that much or all of the tree may go brown. Surprisingly this amount of depredation does not kill the tree, which sends out leaves as normal the following year, but I imagine that it must be considerably weakened over the years.
The caterpillars pupate, and spend the winter within the fallen leaf. The adult moth emerges in spring, a narrow winged moth, reddish-brown with three white cross stripes (does that make it sound as if I’ve ever seen one?). It is small, some ¼ inch long, about the size of a clothes moth. Apart from the damage it does, the most dramatic thing about this insect is the rate at which it has spread, since it first appeared here from the continent as recently as 2002. It already occurs over most of England and much of Wales. Presumably it spreads due to adults being dispersed by the wind, and dead infested leaves being accidentally transported. Infestation may be reduced by collecting and destroying fallen leaves. Interestingly, some trees, especially the red flowered variety, seem to be much less prone.
At the time of writing, there are still a small number of Swallows in the air over the villages. Some of these may be birds with late broods, or they may be from further afield on their way south.
I have written before about Robins at this time of year. They make themselves very conspicuous with a sharp ‘tic tic’ call, and especially the fact that in autumn and winter, unlike other birds, they sing. Singing in spring is a sign of advertising and defending a territory in which the pair can breed. In winter a similar territory is occupied by only a single bird. The young of the year and one of the pair, most often the female, are driven out. These birds move away to find an empty territory, or may even migrate across the Channel. The remaining bird will sing, and many people detect a thinner, more wistful quality than in the spring. Early next year a partner will turn up, often the previous mate if it has survived.