Why this raptor is barely hanging on

Golden eagles and kites are back in Ireland, but another native bird of prey is in danger of extinction here, writes ANTHONY KING

EFFORTS TO reintroduce golden eagles and kites in Ireland have grabbed headlines but another raptor also deserves public attention. The hen harrier is barely clinging on in the countryside, with fewer than 130 breeding pairs remaining.

University College Cork’s Dr Barry O’Donoghue has tagged and tracked harriers and studied their diet and distribution for his PhD project, the first on a native bird of prey in Ireland. His research adds to our understanding of its ecology, crucial if we are to save this endangered species.

Special Protection Areas (Spas) for harriers are in upland habitats of the southwest and midlands, such as in the Slieve Blooms. In Springtime the conspicuous gray-blue males free-fall, roll and spin in spectacular “sky dances” to impress females.

The months outside the breeding season were something of a mystery, but the new research shows how the birds disperse across the country, says ecologist Prof John O’Halloran of University College Cork, project supervisor. “Barry’s work shows coastal areas are really important during this time.”

Typically the birds prefer marshy fen areas in winter, but they can be encountered in almost any county, O’Donoghue has found. “You’ll find them on tillage areas in east Cork, Waterford, Wexford in particular and even up to Louth. They hang around stubble fields where they can catch rats and mice.”

Thanks to over 250 volunteers in the Hen Harrier Winter Roost Survey, 81 roosts have been located and we’ve a good picture of harrier activity, adds O’Donoghue, who is a ranger in the National Parks and Wildlife Service.

“Usually our roosts have three or four harriers, but there can be up to a dozen. Seeing them coming in on winter evenings over the snow, criss-crossing one another, gliding, and playing around is really beautiful.”

Harriers are ground nesters, using heather moors and scrub in Ireland. But the Irish birds are unique in Europe in that they nest in forests too. Whether that bodes well for them is an open question.

“Hen harriers have taken to nesting in young forestry plantations, which have replaced heather nesting habitat in many places. Those birds are more prone to breeding failure due mainly to predation,” says O’Donoghue.

“Just because a bird is living in certain habitats doesn’t mean it is ideal. They may have no choice.”

The birds use second rotation forests up to 12 years of age – Christmas tree size – but stop when they age and close in. The researchers warn that it is crucial that Irish estate forests are of mixed age in any one area if hen harriers are to persist. Diversifying forest structure is also important.

One mystery identified after recent UCC research is especially disquieting, says O’Halloran. “We have tagged 150 [nestlings], but we are not seeing them coming back into the population. That is astonishing. They might not be surviving or they might be migrating. Or birds coming in from Scotland and Wales could be supplementing our losses.”

O’Donoghue recalls trips during his youth to east Kerry where there were 10 or 12 pairs. “In 2010, after years of steady declines, the last pair of harriers vacated this area and in 2011 we may be looking at no harriers there at all,” he says.

“That is reflected across the country. Wicklow would have been one of the strongholds of hen harriers, but they don’t breed there any more.” He says harriers are an indicator species for a healthy environment.

He believes it would be impossible to reintroduce hen harriers if they went extinct because it is so difficult to row back on habitat loss. And this harsh winter adds to his concerns: “This winter there are so many roosts that aren’t occupied and casual sightings have been way down.”

In the UK, harriers are often shot on commercial grouse hunting moors, but persecution is not a problem here. O’Donoghue found just one grouse among 2,000 hen harrier prey items he examined. Irish birds prey mainly on meadow pipits in upland areas, and in lowlands they catch rabbits, hares, small birds and shorebirds in winter.

Harriers are protected as an Annex I species, the top notch in conservation stakes.

HEN HARRIERS

Hen harriers ( Circus cyaneus) are medium-sized raptors with striking differences between the male and female. The larger female is mainly brown with pale underwing markings and a white rump, while the male is white and silver in colour, with black wing tips.

They hunt small mammals (mice, rats and voles) and other birds, by gliding low over the ground, their long wings held in a shallow V-shape.

They breed in the uplands in spring and summer, especially counties Laois, Tipperary, Cork, Clare, Limerick and Kerry. Food is transferred aerially between male and female by means of a “food pass” whereby the female somersaults upside down to take the food from the male’s talons.

The species has declined both historically and recently due to land use change by forestry and agriculture. Their name in Irish is Cromán na gCearc. Readers with recent sightings of the bird should report them to Barry O’Donoghue at harriers@environ.ie.