The impact of changes in land-use in Orkney, on the vole Microtus arvalis orcadensis and its avian predators
The microtine rodent Microtus arvalis orcadensis is endemic to 5 of the Orkney Islands. Aspects of the ecology of this animal were studied on Mainland Orkney during the period June 1988-December 1990. Subject areas included habitat-related variations in population density, social organisation and short-term and seasonal variations in activity. The importance of the Orkney Vole in the diets of Hen Harriers, Short-eared Owls and Kestrels was quantified and assessed, both in the context of optimal foraging theory and in relation to the contribution made by female avian predators to nest provisioning. The selection of hunting habitat by avian predators, in relation to spatial variations in vole population density and temporal variations in vole activity was also considered, particularly with respect to Short-eared Owls. Using land-cover data derived from air-photo interpretation, estimates of the total population of Orkney Voles were made and the implications of changing land-use for the conservation of both Vole and avian predator populations considered. Specific types of land management are proposed to ensure that populations of both the Orkney Vole and the avian predators which depend to a varying degree upon them, are effectively conserved.