Rural: nature notes

Stand still for a few moments in a beech wood at this time of year, and you are likely to hear a pitter-patter of debris falling from high in the tree canopy.

The source is bound to be a grey squirrel, shelling nuts either for immediate consumption or for winter storage. This year's huge harvest of beech mast is bad news for foresters. Abundant food will step up the squirrels' breeding potential and increase their destructive bark-stripping next May, June and July.

The greys do little damage in their native North America, but since being imported here in the last century they have become a menace, driving out the smaller, more attractive red squirrels and crippling millions of broad- leaved trees - yet another illustration of how unwise it is to move species into alien environments.