Why do hen harriers find Ireland so hard to live in?

ANOTHER LIFE:'AT HIGH INTENSITY, male appears to follow path of invisible coil-spring, seen from end of coil, clearly loops-the-loop, and twists at top of each loop, upside-down momentarily – like stunting aeroplane performing barrel-roll." Thus the ultimate "sky dance" of the courting hen harrier in spring, as conjured in The Birds of the Western Palearctic, the massive and meticulous magisterium of western ornithology.

"Using a ground tracking device, and my dog Mel, we set about homing on the tag location, in fiercely difficult scrub and swamp. Finally, we found Blackwater's remains, with the tag still attached. Only bones and feathers remained of what was once such an inspiring and awesome creature." Thus the passing of a female hen harrier this autumn, somewhere east of the Boggeragh Mountains, in Co Cork, a bird named by the schoolchildren of Duhallow and discovered by Barry O'Donoghue, conservation ranger with the National Parks and Wildlife Service and leader of the tracking of local harrier lives. In henharrierireland.blogspot.comhe told the children, too, about the fate of Sky, the young male found just a few hundred metres from his nest (where a fox scat hinted at his end).

The dead birds – two of four tagged in August – had, he consoled, done their species some service, confirming “just how difficult harriers are finding it to get a foothold on the Irish landscape”.

Hen harriers are, indeed, rare. I once watched one soaring as I cycled through the Slieve Blooms – a silvery, black-tipped male – but missed the bigger, tawny female that quartered my own hillside in winter while my back was turned.

The last big field survey, in 2010, estimated that Ireland has only 200 or so pairs of harriers, breeding mostly in the rougher, forested uplands of the southwest. Their population was reckoned stable overall but still “of high conservation concern” and warranting the special protection areas called for by the EU birds directive. The birds are declining in three SPAs and increasing in three others.

The crisis is one of replacement. Of about 180 harriers wing-tagged in the Republic since 2006, just four have been known to breed; birds similarly tracked in England and Scotland have established themselves in the landscape, unbothered by predation or shortage of food.

Evidence from wing-tagging suggests that four out of five Irish harriers die before their first birthday. Rows about the birds having to live with whirling wind turbines certainly matter when numbers are so small, but the basics of bird survival – food supply and habitat – are still what count most.

The hen harrier, Circus cyaneus, feeds on little birds and field mice. (Its appetite for baby grouse accounts for its absence from Britain’s closely keepered moorlands.) The Irish birds show a strong new preference for nesting in young (“prethicket”) conifer forest planted on clear-felled land for a second rotation. The adaptation has been forced on them, as conifers replaced the open moorland where the birds used to nest in heather – this, too, so often erased in overgrazing by sheep.

They still need open country for their foraging, however, as they roam widely in search of prey. So the spread of conifer forestry might seem one of the worst changes in land use. But a new report from Planforbio, a scientific group at UCC that studies ways to manage forests for biodiversity, suggests “the overall effect of plantation forests on breeding hen harriers in Ireland is positive”. It could even get more so, the study suggests, as farmed trees replace grassland of little value to the birds.

Fragmentation of the uplands, however, is foremost in Barry O’Donoghue’s mind as he weighs the loss of Blackwater and Sky. “This summer,” he writes in his blog, “we witnessed parent birds travelling massive distances over forestry before they even reached their hunting grounds, and there were days when chicks may have received just one food item in a day, whereas they should have received around 20 . . . Many nests in Ireland did not rear any chicks at all this year due to lack of food and predation.” Even harder, then, for the newly fledged young to find food when, after three weeks of parental nourishment, they are left to fend for themselves.

Meanwhile, O'Donoghue and his fellow researchers press on with another winter survey of hen harriers at their communal roosts, often in coastal reed beds. This, he enthuses, offers "many amazing and unforgettable moments", from seeing seven or eight birds in the sky at sunset to "watching harriers perched on ice-capped fence posts". With co-ordination by the National Parks and Wildlife Service, surveys by teams of volunteers have located more than 80 winter roosts, and any sightings of hen harriers between now and March will be eagerly received at harriers@ahg.gov.ie.

Eye on nature

On a forest path I came across several little piles of rowan berries looking as if they had been regurgitated or excreted – at any rate only partially digested.

Tom Wilmot, Ballyshannon, Co Donegal

Probably excreted by a pine marten, which are known to gorge on rowan berries.

I watched 12 ravens fly from the sea at Ross westwards towards the uplands. I usually see them alone or in pairs. I see the collective nouns for ravens are a conspiracy, murder or unkindness, and even a storytelling.

Denis Quinn, Killala, Co Mayo

Juvenile ravens flock after breeding season, but ravens also flock if there is a source of food around.

I found some shellfish on the beach near Hook Head, Co Wexford, attached to one another with black tubes, firmly attached to a plastic container and still breathing. Heather Dunwoody, Blackrock, Co Dublin

They were goose-necked barnacles, which float about in the ocean until they find a solid object on which to fasten.

On a recent dive in Mulroy Bay, Co Donegal, Sheephaven divers observed two separate pairs of very large mature lobsters fighting most likely for territory. You can watch a video of them at youtube.com/user/SheephavenSAC.

Dearn McClintock, Letterkenny, Co Donegal

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo, or email viney@anu.ie. Please include a postal address