The hen harrier is listed under annex 1 of the Birds Directive 79/49/EEC which imposes an obligation on member states to protect and provide for special measures for conservation of wild birds. The birds directive was transported into Irish law by the Wildlife Act, 1976, as amended, and the hen harrier is a protected species under the Wildlife Act, 1976. It is an offence to hunt, disturb or destroy the hen harrier, its nest or its eggs. While no specific sites have been proposed for designation for the hen harrier under the birds directive – special protection areas, or the habitats directive – special areas of conservation, this species benefits indirectly from the sites proposed for designation in Ireland under both EU directives.
Breeding hen harriers were surveyed nationally in 1998-1999. A supplementary survey in two poorly known parts of the range in 2000 and 2001 is ongoing. The total number found by the end of the 2000 field season was 89 confirmed and probable and 25 possible breeding pairs. Almost all pairs bred in the south midlands and south-west of the country. Only 6% of confirmed pairs bred elsewhere in counties Donegal and Monaghan. Numerically the most important hill ranges are the Mullaghareirks-Stack's where there are 29 to 36 pairs, the Slieve Aughties which has 11 to 18 pairs, the Slieve Blooms which have ten to 11 pairs, Slievefeelim-Silvermines which has seven pairs, Ballyhouras which also has seven pairs, and the Kilworth and Knockmealdowns which have five and seven pairs. Other areas held five pairs or less. The 1968-72 breeding population of hen harriers for all Ireland was 300 breeding pairs. Since then although the species has declined in numbers and its range has contracted some recovery has taken place in recent years.
Hen harriers show a fairly wide choice of nest site and their main requirements seem to be for a dry site, well hidden in tall vegetation. During the survey nests were found in unplanted heathland, newly planted conifers, young second generation conifer plantation and in deciduous scrub growing in gaps and ride lines within conifer plantations. Suitable nesting opportunities are likely to be widespread. The increase in afforestation in recent years has provided increased habitat for the hen harrier.