The following update was written by Michael Walter:
It has indeed been a strange end to the season, summer sometimes flaring up for a beautifully warm, sunny day, with surprisingly good numbers of butterflies (mainly red admirals and commas) right through to the end of September. I also seem to have been aware of more moth caterpillars than usual, two of the more dramatic ones being elephant hawk moth and vapourer. The hawk moths are a group of mostly large insects with correspondingly fat larvae, and the elephant hawkmoth is no exception. This means that it would potentially make a very tasty meal for many insectivorous predators, but it has evolved two rather striking, linked defence mechanisms. On the front of its head are painted two patterns that look remarkably like large eyes. These presumably serve to frighten the predator, but by itself this subterfuge might not prove too effective, so the caterpillar has developed a supplementary defence whereby, on sensing danger, it can inflate its head so that the "eyes" suddenly look far bigger and more menacing. The front of the head also has a curious appendage which blows up to look like a nose or trunk (hence the epithet of elephant in its name). Another interesting insect I've seen recently in the wood is the larva of the vapourer moth. The smallish adult is orangey-brown, but the caterpillar is covered in long, black irritant hairs, some of which are clumped into false antennae and a tail spike. Red spots are lined up along the sides, but its crowning glory is a row of four flat-topped, yellow clusters of bristles that make the caterpillar look for all the world like a miniature toothbrush!
Conifer thinning is due to begin in the reserve today (13th October). Scattered through the wood are a number of conifer plantations, mostly Corsican pine which, as you might guess from its name, is not native to this country. Conservation organisations generally take the view that alien plants and animals should be removed where feasible, hence the campaign to eradicate the ruddy duck (which is threatening the survival of the rare white-headed duck by hybridising with it), and attempts to kill off Japanese knotweed, which can choke out all other vegetation. Unlike those two examples, Corsican pine is not invasive but, in establishing it in ancient deciduous woodland, foresters in the 1960s effectively destroyed that more primordial habitat. So, over the years, the RSPB has been gradually thinning out the pines, a "softly softly" approach which can be less environmentally damaging than wholesale removal of the conifers in a single operation. This latest thinning should have been carried out four years ago, and the failure of the work to go ahead is testament to the perils of over-reliance on modern technology. Nowadays conifer felling is normally carried out by a single operator working from the warm cab of a machine called a harvester. This is essentially a tractor with vast wheels and a complex crane assembly whose head can grab a tree at its base, cut it (either with a chainsaw attachment, or with a pair of hydraulic shears), swing the tree down to the ground in any desired direction, strip off the branches, and cut the trunk up into lengths (the cutting head can detect the diameter of the trunk, so thinner sections can be cut into longer or shorter lengths than the fatter parts) - all achieved in the space of a few seconds. This wonderful capability is controlled by an onboard computer, so when the machine arrived on site in 2010 but promptly had its electronic heart vandalised, resulting in £20,000 of damage, the monster, now reduced to a useless wreck that could not even turn over its engine, had to be towed away to its base in Norfolk.. Hopefully, nothing untoward will happen this time!
Elephant Hawkmoth caterpillar
Vapourer moth caterpillar