THE first Scottish reference to the hen harrier comes in The Fenyeit Friar of Tungland, a Middle Scots poem by William Dunbar. It’s the satirical tale of a false Italian abbot, John Damian, who tries, Icarus-like, to usurp the birds’ domain in false feathers. Dunbar, who is of the birds’ party, describes how the wildfowl set upon the charlatan “with a yowle”. In their number are “The myttane and Sanct Martynis fowle”. The latter name – as le busard Saint Martin – is still used in France, in reference to the time of year when this most elegant raptor appears. The former name is more puzzling, but almost certainly points to the larger “ringtail” female which for centuries was considered to be an entirely different species.

In the north-west of Scotland, the hen harrier is known as the Clamhan Luch, or Mouse Hawk, and it used to be considered good fortune to see one in the morning. Not such good fortune for the harrier if it was seen by a gamekeeper. The Gaelic name suggests that the bird was considered innocuous where there was no poultry, or no population of maintained grouse, to protect. Where that was the case, the bird was persecuted almost to extinction. By 1900, it was limited in Scotland to Orkney, the Uists, Benbecula, South Kintyre and Arran, where my grandfather watched them as a boy. The Scottish population, which is now by far the largest in the UK, only began to recover during the Second World War, when gamekeepers were diverted by shooting Germans rather than raptors.

Donald Watson’s unflinching recitation of avian massacres reads harshly now, as does his almost affectionate characterisation of the egg collectors who followed. Different, but not necessarily higher, standards apply today. Before modern optics were introduced, the only reliable way to identify and study birds was to shoot them or take their eggs and young. The reason the ringtail/white hawk distinction lasted so long was that early observers mistook the famous food-pass from male to female as a squabble over territory by different species. The bird is now protected, but individuals are still killed, even though the evidence about grouse and poultry predation isn’t absolutely rock solid.

Like Mark Avery, who contributes a foreword to this new edition, I’ve had a copy of the T&AD Poyser first edition since 1977. Its handsome white cover is marked with handling and the opening chapter, a brilliant exposition of how to distinguish the hen harrier from the Montagu’s, the marsh, and the equally beautiful pallid harrier, is covered in fingerprints and pencilled annotations. As are some of Watson’s paintings of the birds, technically naïve, but absolutely true to the spirit and “jizz” of the species. Time to meet the male bird, though more people have seen one than realise, because it is quite possible in low light to mistake it, with its pale plumage and black wing-tips, for a gull working a field. The actual colour is somewhere between white, grey, ash and blue, all names that have attached to it locally. The giveaway, apart from the long tail and trailing feet, is the strangely awkward flight, to which the poet John Clare, a passionate bird man, lent the adjective “swopping”, which combines “swooping” and “flopping” in exactly the right measure. A male hen harrier in glide is as impressive as a stealth fighter. I once saw one, armslength-close, from the seaward hide at Caerlaverock, and it was a moment that burrowed deep inside. The eye colour was paintbox yellow, indicating an adult bird, but suggestive of wildness. The day this new edition turned up at the house, a local “ringtail” flew parallel to the car for half a mile, alternately “swopping” and gliding close over banks of rashes. Always a great sight.

Watson did his main research far from John Clare’s East Midlands, on the open moors of Galloway, but he brought to his observations a first-hand knowledge of other world harriers, notably the showboating pied harriers he observed from a gunnery position in Burma during 1944. Pieds have their admirers, but even after seeing them in Pakistan, I haven’t changed my view that the hen harrier is the real star of the family. To describe it as misunderstood is a serious understatement. Harriers also kill rats, mice and rabbits. Clare disloyally lists the diet as “leverets, partridges and pheasants” and it is the latter two courses that have made the bird public enemy number one wherever plus-fours are worn. We’re in more enlightened times than Watson’s, and very largely thanks to his devoted efforts, but the case isn’t won just yet. Every time one of these magnificent birds is taken by shotgun or trap, the sky weeps a little.

The Hen Harrier by Donald Watson (foreword to the new edition by Mark Avery) is published by Bloomsbury, priced £18.99