Use of dwarf shrubland–grassland mosaics by a nomadic predatory bird: the Short-eared Owl Asio flammeus

The constituent habitat use by remotely tracked tagged Short-eared Owls Asio flammeus on moorland and other dwarf shrubland–grassland mosaics was assessed in Britain and Norway. A preference for the owls to hunt over patches of graminoids within managed moorland in Britain contrasted with a tendency to hunt more over dwarf shrubs in Norway. The observed differences likely reflect the availability of small mammal prey and how this contrasts between largely single-species stands of managed heather Calluna vulgaris in Britain and more naturally diverse (species and structure) dwarf shrubland in Norway. Diurnal patterns of landscape use differed between areas, with owls in Scotland and Norway tending to hunt over ground at higher elevations at night but the reverse being observed in England. The difference demonstrates behavioural plasticity of Short-eared Owls, potentially driven by minimising risks from predation within different areas. Conservation implications include increased and proportionate priority for grassland management on British moorlands and the restoration of natural montane dwarf shrublands, both routes to enhance conditions for and the availability of small mammal prey. As a generality, site protection for Short-eared Owls and their monitoring need to acknowledge uncertainties around variations in abundance and occupation by this nomadic species.