The harassed harrier

HEN HARRIERS are in the news. As Gordon Deegan reported in The Irish Examiner last week, the developers of a €10 million windfarm in Co Clare have been asked by the Department of the Environment to incorporate measures to protect harriers.

These magnificent birds of prey are also in trouble in England. Richard Saunders of the Royal Society for the Protection of Birds, speaking on BBC Radio 4, claimed that only 12 pairs of hen harriers bred in England this year and most nesting attempts failed. The birds started to nest and then suddenly disappeared. Foul play is suspected. The English population is confined to the grouse moors of northern counties. Harriers take grouse chicks and shoots are big business. Game-keepers are almost certainly responsible for the harriers' demise.

The hen harrier is a large hawk with a long tail. The male, blue-grey all over with black wingtips, could almost be mistaken for a gull. The female, bigger than the male, is dark brown. Both sexes have a conspicuous white rump, making it easy for birdwatchers to tell hen harriers apart from other birds of prey. The flight too is characteristic; harriers fly low with their wings held in a shallow V.

As its name implies, the bird used to attack farmyard chickens. It is hard to believe that they ever did this because, nowadays, harriers tend to avoid human settlements. The Irish name is préachán na gcearc, the 'crow of the hens'. Could the bird have have been confused with the grey crow, which does take chickens?

Male hen harriers, after all, are grey like the crow. At any rate, farmyard fowl have nothing to fear nowadays. Harriers live mainly on mice, rats and small birds. Elsewhere, voles feature in the diet. Until the 1960s, there were no voles in Ireland and they are still largely confined to Munster.

Irish harriers frequent mountain blanket bog, although they will venture onto farmland when not breeding. Last month, I came across one hunting over fields in North County Dublin. The sighting was a stroke of luck because the hen harrier is rare around here. In 1900, hen harriers were relatively common wherever the habitat was suitable and they were recorded breeding in 19 counties. In those days, landowners persecuted birds of prey and, within a few decades, the harrier was almost extinct. In his List of the Birds of Ireland, published in 1937, George Humphreys wrote that the hen harrier was 'still probably resident in a few of its original haunts, the wilder mountain districts'. Then, from about 1950 onwards, the situation began to improve.

The Cork ornithologist, Liam O'Flynn, documented the change. By 1964, at least 34 pairs were nesting in six counties. The birds which recolonised Ireland probably came from Scotland where there are between five and six hundred pairs. Harriers, in this part of the world, are not migrants in the ordinary sense but young birds disperse southwards after fledging.

The widespread planting of fast-growing American conifers in Ireland has been much criticised by environmentalists and with good reason. However, O'Flynn believed that the new forests benefited harriers. They may even owe their survival here to the plantations. Ground cover, when the trees are very young, is thick and varied, providing excellent protection for harrier nests and making it harder for foxes and other ground predators to find them. Songbirds, which thrive in the young plantations, are a ready source of food for harriers.

But as the trees mature the ground cover disappears and so do the harriers. Harriers returned to Wicklow soon after tree planting began in the early 1950s. In the 1960s, according to the late David Scott, there were up to 20 pairs nesting in Wicklow. Then the trees matured and numbers declined. Harriers no longer nest in the county.

The most comprehensive survey of the harrier population in the Republic was carried out by David Norrris, John Marsh, Don McMahon and G. A. Oliver between 1998 and 2000. The number of nesting pairs recorded in the survey was 102, with a further 27 for which breeding was not confirmed. The population density was similar to that found during the breeding bird survey ten years previously, so the birds are holding their own. According to the Irish Raptor Study Group, there are between 200 and 250 harrier pairs in Ireland as a whole.

Now a new threat has appeared. Ireland is one of the windiest countries in the world and windmills are an ideal source of renewable energy. The best windmill sites, however, are on hills and some of those chosen to date are frequented by harriers. Turbine blades can strike birds, although this is more likely to affect migrants passing through an area than those which are resident. Adult harriers living near windmills soon become aware of the danger and avoid the blades. The noise from windmills, particularly when the wind is strong, should warn off the birds, although the occasional inexperienced youngster may be vulnerable. Disturbance during the construction of windfarms is a more serious problem, but, once the mills are up and running, this may not be an intractable problem. Provided that they are not persecuted, hen harriers can become quite tolerant of people. In Norway, for example, they nest close to human artefacts and there is even a record of a pair nesting 10m from a railway line.