Habitat use by Hen HarriersCircus cyaneuson Orkney: implications of land‐use change for this declining population

The use of habitats by hunting Hen HarriersCircus cyaneusjust prior to the settlement period was investigated on Orkney, where numbers have declined by 70% over the last 20 years. Both males and females hunted over areas that were closer to subsequent breeding territories. Neither sex differed in the amount of time they hunted over areas dominated by either intensive pasture, moorland or rough grazing. However, male hunting was significantly related to the amount of unmanaged grass habitat with a litter layer. Female hunting was related negatively to vegetation height, and to the prevalence of both HeatherCalluna vulgarisand managed grass; after controlling for these habitat features, female hunting also tended to be associated negatively with Common StarlingSturnus vulgarisabundance. Dramatic changes in land use on Orkney have occurred over the last 40 years, with increases in the amount of intensive pasture and decreases in the amount of rough grazing. These changes, coupled with a doubling in sheepOvis ariesdensities over the last 20 years, are likely to have reduced the amount of unmanaged grass. These changes will have been detrimental to hunting male Harriers by reducing the amount of food they can supply to the females prior to egg laying and during the incubation period.