The burning, which starts in October and continues until April, should produce a mosaic of burnt areas (an area burnt this year, last year and so on), the areas becoming greener and greener as the heather regenerates, with the edge of each burn ragged rather than straight. During the first fortnight after they leave the nest, grouse chicks feed on insects and wander into the open, and ragged edges gives them a chance of escaping a hunting hen harrier while a straight edge leaves them totally exposed.
The sun was low over the horizon as the male hen harrier crossed the River Ribble and flew up into the Forest of Bowland. Smoke from heather burning was still drifting across the moors and fells, with men in lines tending the edge of the fire. He turned sharply to avoid them, as last year he’d lost three primary feathers to a shotgun blast. He flew straight to one of his favourite hunting areas, an open area of fell well covered with grass. He saw the occasional sheep grazing contentedly, but they took no notice of him. Eventually he found what he was looking for, a marshy area from which sprang a rill that eventually fed into the Ribble. He dropped down until he was about ten to fifteen feet off the ground and began a methodical search for prey into the wind. Flap, flap, flap, glide.
At the end of the marshy area he turned and drifted down with the wind, a V-shaped silhouette that hovered now and then to investigate a movement or a sound. By the rill were several stands of rushes. He heard a squeak and hovered over it, his ears hidden behind the owl-like mask of his face picking up the rustle of movement through the rushes. He extended his long yellow legs, closed his wings and dropped down. His eight black, needle-sharp talons unerringly grabbed the prey, a short-tailed field vole.
Short-tailed field voles thrive in any patch of land or field where there is rough, tussocky grass. Mainly nocturnal, their presence is indicated by holes in grass tussocks where they nest, runs in the grass with holes where they pop up from time to time and remains of grass clippings that they have chewed. Both male and female field voles mark their territory and defend it with splashes of urine. It is estimated that there are 75 million field voles in the British Isles, and their breeding season starts in April or May, continuing through to September or October. A succession of litters is produced, with an average litter size of five, and young born at the start of the breeding season will themselves breed later in the same year. Their breeding success follows a cyclical pattern, a poor year followed by a better one. Then, either in the third or fourth year, there is a peak breeding season. This cyclical pattern is exploited by predators in the good years and has a depressing effect on their productivity during lean periods. Research has shown that peak vole years influence hen harrier numbers, with bigger clutch sizes and number of chicks fledged. Small mammals make up a modest but important part of the hen harrier’s diet throughout the year, and two voles would meet the daily prey requirement of a harrier.
Volume 3 of The Handbook of British Birds, 2nd edition, which I bought as a young boy in 1944, gives a concise list of birds’ prey items. The handbook states that the hen harrier:
preys chiefly on birds and mammals taken by surprise on the ground. Mammals include young rabbits, leveret, mice, field- and water voles, rats, etc. Birds: frequently Meadow-Pipits, Sky-Larks, or young Lapwings; occasionally chicken or duck, Teal, Red Grouse, Partridge, Golden Plover, Snipe, Dunlin: also finches (Linnet, Chaffinch, Snow-Bunting), Song-Thrush, Blackbird, Ring-Ouzel and Stonechat. Snakes (Adder), lizards, slow-worm, frogs, etc., also taken, and eggs or young of ground-nesting birds (Meadow-Pipit, Dunlin, etc.): small fish also once recorded: also Coleoptera.
Eagles, Hawks and Falcons of the World by Leslie Brown and Dean Amadon, published in 1968, tackles the subject from a different perspective. The authors cite one analysis that gives the hen harrier diet as 25 per cent birds, 55 per cent mammals and 29 per cent snakes, frogs and insects. Another nesting analysis gives 31 per cent birds and 69 per cent mammals, with meadow mice predominating. Brown and Amadon state that the hen harrier can occasionally take mammals up to the size of a rabbit, and birds up to the size of a young bittern, but large birds such as ducks are usually wounded or moribund when taken. Food is usually taken on the ground, as the hen harrier can rarely capture birds in the air. Food requirements vary from 100 grams daily for a female (19 per cent of body weight) in cold weather to 42 grams (12 per cent of body weight) for a male in warm weather, the maximum daily intake by a female being 142 grams in cold weather.
Some of the more unlikely species that hen harriers have tackled include hedgehogs and adders, and apart from red grouse hen harriers have been known to take ptarmigan, black grouse, partridge and pheasant. Intra-guild predation has accounted for merlin and kestrel . . . and lastly, an unlucky short-eared owl.
There was no sun and the moor was white with frost when, two days later, the male hen harrier drifted down to Mallowdale Pike ridge in search of a mate. He passed up and down a couple of times, and on the last flypast noticed a female hen harrier in the tall heather tearing at the tussocks of dead grasses below, throwing them in the air. Cautiously he planed down and landed close by. She was larger than him, and in the first glimmer of sunshine he admired her glossy chocolate-brown plumage, noticing the white wing tag with the number 22 in black. He walked over to her. She looked at him and he could feel her sizing him up. Was he good enough? He’d show her.
He rocketed up into the sky. The female watched as his blue-grey outline melded into the now blue sky above. At three hundred feet he turned and plunged into a vertical dive towards her. In freefall he corkscrewed and screamed to attract her attention. Faster and faster he fell. Then, just when it seemed that he would crash right into her, he pulled out and soared up in the air again. He was reckless in his efforts to impress her. Three times he repeated the death-defying plunge earthwards before finally landing by her side. He was panting, plumes of breath hanging in the frosty air. She was impressed and sidled over to crouch submissively by his side. He had found a mate.
‘My routine when I’m checking for the harriers’ arrival,’ says Stephen Murphy, ‘is to drive round to the north side of the central mass of the Forest of Bowland. Here it is split by a valley, and where the harriers nest is way back beyond the horizon. I’ll park my car and watch. This is a muster point for hen harriers looking for a mate. In March and April I have seen eight birds there, all “skydancing”. It’s like a big aerial dance floor, a real sight to behold. When they’ve found a mate, they’ll fly up the valley and up out of sight to where they’ll find a nest site.
‘A week or so later I’ll walk up onto the fell and find myself a spot in the heather where I can scan the distant hillside through my binoculars. At the moment I’m checking one of the traditional harrier nesting sites way across the valley. It’s a favourite site – they’ve always produced young from there. We’re in the last couple of weeks of March and any pairs of hen harriers should be arriving any day now.’
It is the female that makes the choice of where the nest will be, and shortly afterwards she can be spotted flying in carrying grasses or large sprigs of heather or bilberry in her beak, a sure sign that nest-building has started. Starting from scratch, the female chooses a bare area for the nest in tall heather but with easy access to it from one direction. Generally, all the nesting material – from quite bulky twigs to smaller sprays – is picked up within two hundred metres of the nest.
Flying out from her chosen site she pitched on an old heather burn and meticulously pulled