How merlin cast a magic spell on the ranger

Another Life: 'Far away to my right, a muffled and high-pitched chatter revealed a tiny grey flying machine. He scythed through the air, scarcely one metre above the heather tops, at incredible speed. Reaching the head of the brook, he banked sharply to the left and, catching the full brunt of the gathering wind, disappeared into a steep ravine on the south side of Kippure.

Every love affair allows moments of emotion. In the fading light and bitter chill of a February evening in the Coronation Plantation, I allowed myself that time."

Only a merlin flies with such bravura, and only a passionate watcher could record it in such words. Those words come from Merlins of the Wicklow Mountains (Currach Press, £14.99), only 80-odd pages long (including fine illustrations and photographs) but still a milestone book in the history of Irish bird study.

Its author, Anthony McElheron, is a conservation ranger working for the National Parks and Wildlife Service - in fact, he was the very first "wildlife ranger", appointed in 1979. The book shows him digging scraws of peat to make an artificial hummock on the slope of Djouce Mountain. Here he tempted a merlin to pluck its prey in winter - male chaffinches, mostly, with gleaming white wing bars, so much easier to aim for on gloomy November afternoons.

The merlin is our smallest native falcon; the male is not much bigger than a blackbird and weighs a mere 115g. It is the male that stays on the uplands all year round, plucking its prey on post or hummock within sight of its last summer nest and holding its territory in the harshest of weathers.

Merlins that winter bird-watchers see, harassing linnets and waders along the Leinster coast, are nearly always females or juvenile birds.

Even a rough estimate of the national number of merlins could, says McElheron, be wildly inaccurate. Not only are they highly secretive, but human activities have disrupted their traditional ecosystem and forced them into new and varied patterns of survival. Merlins evolved as falcons of heather-clad uplands, preying on meadow pipits and ground-nesting in thick cover. Their biggest enemy is fire. McElheron is savage about "the mindless destruction of vast tracts of pristine moorland", after farmers burned the hills for fresh grazing at the time of high sheep subsidies.

As breeding merlins dwindled in Co Wicklow, the county's maturing plantations of conifers actually came to their rescue. They offered the ready-made nests of grey crows that were scavenging on sheep carrion. The merlins moved aloft, chasing the crows away and choosing nests built in dark Sitkas with some space around them. Today, some 26 of these "islanded" nests are used in the average year - probably as many breeding pairs as the Co Wicklow uplands can presently support.

McElheron's passion for merlins stretches over 20 years, but the core of his book tells of one particular pair, breeding in a storm-damaged Sitka perched above a river on Duff Hill, below Mullaghcleevaun. The birds had used the tree twice, and each time their brood had failed. McElheron began his patient vigils on a bitterly cold morning at the end of March, as the male bird began to court his imperious female partner.

McElheron chronicles the volatile love life of the bonded birds, and the couplings that follow the male's offering of a freshly-killed skylark or wheatear.

Between long sessions at his telescope, he retrieves feathers from plucking posts to record the species killed. Early migrant wheatears are important food and then, as summer warms, exhausted migrant swallows filter through the Wicklow gorges from the east. They arrive during the weeks of the merlins' mating and the male treats them as an easy takeaway, swooping up to grab them from below. Some he brings to his mate; others are stashed in the heather.

The seasonal sequence of food can be surprising. Who would have thought, for example, that merlins needed moths? But the calcium in the insects is essential, especially in eggshell formation, and McElheron finds a hummock below the nest that is heaped with the colourful wings of emperor and northern eggar moths, two of the biggest insects of the heather.

Insects can figure, too, in the male merlin's winter survival. On warm days, midges hatch from pools in the open bog. This tempts little siskin finches to fly out from cover in the dense conifers. McElheron finds their bright feathers scattered on the hummock he built to tempt a male merlin, a success that prompts a whoop of satisfaction.

His summer vigil on Duff Hill, however, has a different sort of ending. What he finds I'll leave to his story.