Country Matters: A dark glimpse of the goatsucker

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WE HAD picked a perfect evening. As the sun set, the wind died to a breath from the west, and only the odd cloud floated in a clear sky. Visibility and audibility were as good as one could hope.

I had come to Wareham Forest, in Dorset, to seek out that mysterious bird, the nightjar. I was in the best of hands, for my companions were Roger McKinley, the Forestry Commission's local environmental manager, and Rod Leslie, another environmental specialist from the commission, with a particularly good knowledge of birds.

Myth has clung to the nightjar for thousands of years. Slim and hawk-like, with a flat head and powerful-looking, hunched neck, it was known to the Romans as caprimulgus, the goat-milker. The bird that visits Britain is still officially listed as Caprimulgus europaeus and, to this day, country people refer to it as the goatsucker - probably because of its enormous mouth, which gapes open in flight to catch insects.

The magic of nightjars is that they perform only after sundown, when the males proclaim their nesting territories by competitive declamation. Once heard, their song is never forgotten, for it sounds too mechanical to be emerging from the throat of any living creature - a steady churring or whirring, which goes on for a minute or more at a time and rises and falls in volume as the bird turns its head from side to side.

For decades nightjars seemed to be declining in Britain. Migrants from Africa, the birds start arriving in these islands at the end of April, to nest on heathland; but their numbers fell progressively to a low point in 1981, when a survey by the British Trust for Ornithology recorded only 2,100 nesting pairs.

The decline was attributed partly to climatic deterioration: cooler, wetter summers - it was said - produced fewer of the moths on which the birds feed. Another reason was thought to be the steep fall in the area of traditional heathland: as more and more open ground was taken for tree- planting, agriculture, houses and so on, habitat suitable for nightjars was whittled away.

Yet the latest survey, carried out in 1992, produced an agreeable surprise. The birds had made a strong comeback, and the number of nesting pairs had gone up by 50 per cent, to more than 3,000. Ornithologists were delighted by this turn of events, even if they were not sure what had caused it.

Research has shown that one fundamental requirement of nesting nightjars is bare earth. The hen bird lays two white eggs in a scraped-out hollow, and although she will sometimes nest in dead brushwood, she will not settle down among growing vegetation. Patches of naked ground are her absolute prerequisite.

This has been convincingly demonstrated by members of the Royal Society for the Protection of Birds in their reserve at Minsmere, in Suffolk. There they scraped out a number of tiny clearings among birch scrub, and so increased the nightjar population from five pairs to 40.

Other researchers, among them Rod Leslie, believe that the apparent decline in numbers may have been at least partly an illusion, and that the birds had not abandoned Britain, but had shifted from traditional haunts to new ground. Not only did huge stretches of heathland disappear - in Dorset 70 per cent vanished - but those areas that remained changed character. In the past, grazing by animals and burning by humans kept the texture of heathland open; but recently, with the removal of animals and lack of active management, trees and shrubs have taken over, leaving no bare ground for nightjar nests.

At the same time, however, attractive new habitat has become available in the form of areas of clear-fell. Still better, in Dorset the Forestry Commission has taken the imaginative step of recreating heathland, by not replanting after felling. Even after 40 or 50 years the seeds are viable, and heather soon starts to grow when light is let in.

A cynic might remark that this land should never have been planted anyway, as it grows only stunted pine. Yet during the 1950s official policy was to plant every square yard available, and the commission's decision not to re-stock, made during the Eighties, represented a considerable breakthrough towards more flexible and creative management. Another benefit of this new policy is that it greatly benefits reptiles - the smooth snakes and sand lizards, for which heathland is essential.

ALL this we discussed as we drove out through the forest. Then we parked the vehicle and walked over the crest of a hill into a wide, shallow depression known as The Decoy, which was clear-felled in 1980-81, replanted, then cleared again last year, to become permanent heath.

We waited for a while, talking in whispers, as the light faded. Thrushes and robins were still singing from thickets on a ridge to our right. Stars began to show in the bright evening sky. Rod explained that only the male nightjars sing: females would be on the ground, already nesting, or preparing to do so. He described how members of the Stour Valley Ringing Group fitted some nightjars here with radios, and discovered that the birds fly up to two miles out of their territories to feed . . .

Then suddenly we heard it, from far off to our left - an unmistakable churring, answered almost at once by a louder whirr from the ridge. Cupping a hand behind each ear, Rod advanced rapidly, hoping to pick up the high-frequency cheep or the clap of wings that males give to warn off rivals during territorial flights.

As we moved forward, still more churring started up, until song was coming from every direction, rising and falling hypnotically. Presently we could identify five different singers, all stationary. Then ahead of us a dusky shadow slipped off the top of a high seat, built for deer control, and flitted away, scarcely visible against the darkening heather.

In low murmurs, Roger began to tell a hair-raising story of how, late one winter evening, he had come out to this valley to check the bonfires on which he had been burning up lop-and-top during the day. A forester all his life, he had been out in the woods thousands of times at night without ever a twinge of fear; but this time, unaccountably, his dogs growled furiously and cowered at his heels, and he himself felt so menaced by some evil presence that he abandoned his task and ran . . .

At that moment Rod suddenly cried, 'Look]' I jumped, but all he had seen was a shadow speeding over us - a slender, streamlined shape, black against the sky, with pointed wings and all its weight up front. For a moment I got my binoculars on to it and rejoiced in the fact that I had had my first good view of a nightjar in more than 15 years.

But as we walked back in the dark, I found myself haunted by the image of Roger's spaniels refusing to leave his side, and the sinister feeling that had driven him headlong from the forest that foggy night.