A mysterious killer stalks the moors: The sinister destruction of two of Britain's rarest birds of prey clouds the start of the grouse shooting season next week. Oliver Gillie reports

TERRY PICKFORD was the first to notice the Land-Rover following us. He pulled over and parked the car on the grass verge. The Land-Rover turned up a side road and then edged out so that the driver could watch us.

We were in the Forest of Bowland, 400 square miles of moorland north of Preston, Lancashire, to check on the breeding success of the peregrine falcon and the hen harrier - two of Britain's rarest birds of prey.

Local gamekeepers keep watch for people who may trespass on the moors. We were wearing green camouflage jackets to evade observation, but it seemed that we had been spotted before we had started.

Terry Pickford and his friends Carl Smith and George Day have been watching raptors (birds of prey) since they were at school. They met on the moors and, determined to guard the birds they loved, formed the North West Raptor Protection Group. This season has been the worst for these birds since the group began making observations in the Forest of Bowland more than 20 years ago.

The Bowland birdmen are not welcome on the moors, so they often have to walk them without permission and risk being prosecuted for trespassing. The moors are jealously guarded by owners who preserve them for the grouse shooting season, which starts next Thursday, the 'Glorious Twelfth'.

The Land-Rover remained stationary. The driver appeared to be waiting for us to make the first move. 'We can't go directly up the road to the moors because they'll stop us,' said Mr Pickford. 'I'll have to drop you beyond the estate boundary and then you can double back.'

The plan was fixed. We set off again and the Land-Rover followed a quarter of a mile behind. But it lagged as we reached the edge of the estate, and as we rounded a spur Mr Pickford briefly stopped the car to let us out. We raced 200 yards to the top of the hill and lay gasping for breath before following a fence, skirting the edge of the Abbeystead estate, property of the Duke of Westminster. From behind some rocks we looked out over the valley and there was the Land-Rover, parked at a vantage point from which the whole sweep of the fells could be seen. It meant we could not take the direct route we had planned but had to make a seven-mile detour to reach a peregrine eyrie among some large rocks on a peak near the centre of the 13,000-acre Abbeystead estate, which covers more than a quarter of the Bowland fells.

The Bowland birdmen have special licences issued by English Nature - the responsible government agency, under the Wildlife and Countryside Act - that allow them to disturb birds of prey if it is necessary to make scientific recordings. But after reporting details of destroyed nests on the Duke's estate to the police last year, their licences to disturb birds there were rescinded. English Nature warns licence-holders that if they trespass their licences may be withdrawn.

The peregrines had made a shallow scrape on a ledge of rock, a typical falcon nest. Fresh splashes of lime and traces of feathery down in the scrape showed that it had been occupied recently. But the eyrie was deserted. There was no sign of the birds.

'If the nest was occupied the birds would be flying around above us. You can't miss them,' said one of my companions. He pointed to a tunnel trap set within a few yards of the nest to catch stoats and weasels. 'That should not be here. Stoats and weasels spend most of their time in the gulleys beside the streams. Gamekeepers coming to check the trap may disturb the falcons.'

The Bowland birdmen have become expert at reading sign. A feather, a splash of lime, a broken sprig of heather provide clues that tell a story. The presence of down in the nest on the ledge told them that at least one egg had been laid because the hen bird does not shed down until it begins to lay. And the presence of relatively few fresh carcasses at plucking posts, where the birds bring their kills when the eggs are being incubated, told them that the birds probably disappeared before their clutch was completed.

'If the eggs are taken within two weeks of nesting, then the birds will lay again. There is a narrow period in which they are able to start another brood if the clutch is destroyed,' I was told. 'These birds must have lost their eggs very quickly, but they have not nested again and are nowhere to be seen. That suggests to us that they have been killed.'

The nest, near the centre of the Duke of Westminster's grouse moor, has failed four years running. At Easter last year some of the Bowland birdmen watched the peregrines at the site perform their courtship in mid-air before mating on a nearby crag. They visited the site in the following weeks and found a nest with down in it - but no sign of the birds. In 1991 the birds survived a little longer but not long enough to raise their brood. Each year the birds at the site have mysteriously disappeared. And similar failures have occurred over several years at another peregrine nest on the estate.

Other strange phenomena have been recorded on the Abbeystead estate this year. Early in May, the Bowland birdmen found the nests of two short-eared owls on moorland about two miles from the main road, one with four eggs and one with two eggs. When they visited the nests a few days later not only had the eggs gone, but the nests had been removed - the only sign that they had been there were a few broken heather twigs.

In other parts of Britain peregrines, although rare, have increased dramatically in numbers since farmers stopped using pesticides which poisoned them. There are now about 2,300 breeding pairs in Britain, double the number 50 years ago. Peregrines even breed successfully in the heavily populated Ribble valley, near Preston, Blackburn and Burnley, where they are close to pigeon fanciers who might be expected to destroy them.

Bowland continues to attract peregrines because the well-managed grouse moor provides a variety of birds, such as lapwing and curlew, for them to feed on, as well as pigeon and sometimes grouse. Improvement in the management of the Abbeystead estate has increased the bag of grouse eightfold since the Duke of Westminster bought the land in 1980. With such a plentiful food supply in Bowland it is difficult to account for the failure of birds of prey to breed in the area. The moors of nearby Cumbria are overgrazed and have fewer birds for peregrines to eat. Nevertheless, peregrines breed there so successfully that surplus birds migrate from Cumbria to Bowland each year.

Rodney Banks, land agent for the Abbeystead estate, said: 'People are obviously breaking the law round about us. We are concerned about all the hysteria and innuendo which is generated by the Royal Society for the Protection of Birds and the North West Raptor Protection Group. We have been quite successful this year with raptors - 24 merlins, two peregrines and three harriers have been ringed on the estate.'

As we completed our inspection of the Duke's estate we spotted the Land-Rover again and so made a further detour of about eight miles to evade any possible confrontation. This enabled us to leave by a public footpath leading through another estate, where Mr Pickford met us - with bad news. He had visited a peregrine eyrie on nearby land owned by North West Water.

'We first saw the nest with the bird sitting on it at Easter,' said Mr Pickford. 'But today there was no sign of the parent birds. They must have been killed because the nest was dry and in good order with three intact eggs. The nest is in a safe place on an inaccessible ledge. There was no reason for the birds to desert it.'

Peregrines have fared exceptionally badly this year on the North West Water estate. On one site stones have been put in a nest smashing three eggs - something that could only have been done deliberately by someone who wanted to prevent the birds from breeding. The maximum penalty for destroying birds or eggs is pounds 5,000 per bird or egg, but there are seldom the witnesses necessary for a successful prosecution.

At another site high on the moors the Bowland birdmen found a nest with the rocks beside it freshly scarred by shotgun pellets. There was no sign of any birds and they could only assume that at least one had been shot. But about three weeks later, in June, they returned to the site and found that two peregrines had established a nest nearby.

The position of this new nest suggested to them that one of the birds survived the shotgun attack to find a new mate and went on to establish the nest in a more concealed location, among the heather. The abandoned nest site was on land belonging to North West Water in Lancashire, while the second site, 500 yards away, was in Yorkshire on another estate. But neither the new position in the heather nor the move across estate and county boundaries protected the birds.

'They rarely nest on the ground in Britain,' said Mr Pickford. 'When we returned shortly afterwards we found down in the nest so they must have laid at least one egg. But the birds had disappeared. We fear they have been shot.'

Early in spring another destroyed nest was found three miles north-west of this site, on the edge of the Mallowdale estate. The Bowland birdmen had come across three kills close together in a gulley, a sign that birds might be nesting nearby. After a search, they discovered the nest 500 yards up a steep slope. It had been filled with stones.

Richard Challenor, land agent for the Mallowdale estate, said: 'I am intrigued to hear that there may have been a peregrine nesting on our land and horrified if it has been interfered with. We love peregrines and they are not a problem. They only take a minuscule number of grouse.'

The Bowland team has sent its records to be collated by the RSPB, which is employed by North West Water to protect birds on its land. The society has records of the destruction of eight peregrine falcon nests and five hen harrier nests in the Forest of Bowland this year. A few pairs have fledged their young successfully, but only a fraction of the number expected. These disastrous results have also been reported to the Lancashire police, which is investigating.

In looking to explain their findings, the RSPB recognises that the only people likely to be motivated to destroy birds of prey and their nests, other than bird haters, are pigeon fanciers and people who want to increase the number of grouse for shooting.

Tim Melling, a spokesman for the RSPB, said: 'The circumstances are suspicious. It is very strange to observe a nest one day and then, a few days later, to find that all traces of it have disappeared, or to find that stones have been piled into a nest stopping that site being used in future years. We are puzzled - we don't know how to explain it.'

Jim White will be back next week.

(Photographs omitted)