Latin name: Circus cyaneus
In Northern Ireland, the hen harrier is most likely to be encountered in the Antrim hills and Fermanagh uplands. The best time to look is in March or April when birds are displaying over potential nesting sites. The population in the Republic of Ireland was estimated at 102-131 pairs in 2000, while in Northern Ireland there were 50 to 60 pairs in 2004. Although small, this population is of both Irish and UK significance and shows an increase from 38 pairs in 1998.
The male and female birds differ in appearance but both have long wings and tails which make them easy to identify. The female is the larger of the two birds and is brown with a barred tail. The male is pale grey with black wing-tips and both have a white rump. Young birds resemble the female and have become known as “Ring Tails”.
Harriers have a distinctive low flight interspersed with frequent glides when they raise their wings into a V shape.
The hen harrier is 45-55cm long with a 97-118cm wingspan. Males weigh between 300 and 400g, while a female hen harrier is heavier - up to 700g.
The hen harrier is most at home in open moorland, where it flies low over the ground in search of prey. In spring the male and female chase and tumble high over the moors and forests in a spectacular sky dance display. The uplands of Counties Antrim and Fermanagh support the majority of Northern Ireland's breeding pairs.
The hen harrier is vulnerable to habitat change, egg/nest predation and persecution.
Hen harriers usually nest on the ground in tall heather or in young forestry plantations. The nests are made from heather stems and rushes and are lined with grasses. Eggs (usually 4 to 6) are laid by late April or early May. Eggs hatch 29-39 days later and the young will have fledged and left the nest after 5 or 6 weeks.
In the autumn the birds leave their upland breeding areas and move to the lowlands or coast where finding food in winter is easier. In winter, hen harriers can be found in a variety of habitats including wetlands, estuaries, coastal and farmland. Favoured sites such as reed beds or forestry plantations can be used as winter roosts.
In recent years in Northern Ireland, hen harriers have been discovered tree nesting in the tops of conifers within plantation forests. This is apparently unique among European hen harriers, and seems to be spreading to other forests in Northern Ireland.
One of the UK's birds of prey, it once preyed on free-range fowl, earning its present name. It favours small birds (such as skylarks and meadow pipits) and mammals. However, it also takes larger prey and has come into conflict with grouse moor managers who blame it for reducing the numbers of grouse on commercial moors. They also feed on small mammals and occasionally reptiles, amphibians and insects.
Hen harriers declined in numbers across Europe between 1970 and 1990. While this decline has slowed, numbers are still lower than before the decline began. They suffer from illegal persecution, particularly where they occur on grouse moors.
They were persecuted almost to extinction in the nineteenth century, but spread due to the planting of forestry plantations which offered suitable habitat and safety while the trees were still young. Overgrazing of uplands and the loss of semi-natural habitats are threats to the hen harrier across its European range. In Northern Ireland, while there is less persecution, it is the threat to the hen harrier's upland breeding grounds which causes most concern. Some proposed wind farm developments are also worrying some people.