Once again, the Swallows and House Martins which nest in our villages have left us, off to their winter quarters in Africa. In the fine summer, many had late broods and some were still to be seen in mid-September. By now they have almost all gone, although a few stragglers may still be seen. Although we know they reach many parts of Africa beyond the Sahara, the wintering habits of British House Martins are very little known. Over the years some 300,000 martins have been ringed as nestlings or by netting. Of these, 70 have been found in southern Europe and north Africa, indicating that they migrate on a broad front. Only one ringed bird has ever been found south of the Sahara, in Nigeria.
Swallows are better known. Of over 1 million ringed, almost 500 have been found south of the Sahara. By October they have reached north Africa and beyond – Nigeria and the Congo – and they spend the winter in South Africa and Namibia. They have been studied there by South African ringers. They do not breed, but it seems that they stay faithful to the same night-time roosts for most of the winter, feeding mainly in the wetter areas. A few ringed there have been recaptured in Britain in the summer.
Bats are disappearing too, but not because they migrate. By November, our bats are hibernating in suitable winter sites. Pipistrelles, for instance, hibernate in small, mixed groups. They become torpid, their body temperature dropping almost to that of their surroundings. Even so, they cannot survive much below 3.5C, so they need to find somewhere which remains a little above freezing point. In the absence of hollow trees in a village, this usually means a roof space or some other available part of a building. Occasionally in winter, during a warm spell, a Pipistrelle may briefly come out of hibernation and be seen flying around, even in daytime. As there will be little insect food available, it will soon have to return to its roost so as not to use up its energy supply.
Another scarce small mammal turning up as prey in the pellets of Sweffling Barn Owls is the Water Shrew. Not often seen, this is our largest Shrew, about the size of a mouse, black above and white below. It has some subtle features which allow it to swim and hunt in water, without being an inconvenience on dry land. For instance, along the sides of each toe is a fringe of stiff hairs which in water fan out between the toes to act just like a web. Interestingly, although Water Shrews have been taken by the owls hunting the meadows here along the Alde, there are none so far from the fields on higher ground in the north of Rendham.
Among the most conspicuous of the insects at this time of year are the Craneflies, most often known as ‘Daddy Longlegs’ from their enormously long and thin angling legs. In mid-September, these flies were hatching in large numbers from lawns and fields where their larvae, the fat grey grubs known as ‘Leatherjackets’, feed on roots. They are an important source of food for probing birds such as Blackbirds and Starlings. Craneflies often come to lights or inside houses. There are many species, the males with the blunt tails and the females with pointed ends used in laying eggs in the soil. They are quite harmless, although perhaps not always welcome indoors.
By Geoffrey Abbott