Nest site selection by Hen Harriers in Scotland.

Abstract

The aim of this study was to examine nest site selection by Hen Harriers Circus cyaneus at two spatial scales in Scotland and to assess whether breeding success was influenced by choice of nest site. At the landscape scale, we compared availability and utilization of habitats in 610 km² of Argyll, and at the local scale, we compared vegetation and topography at 52 harrier nests and random points within three areas of heather moorland covering a total area of 462 km². At both scales, harriers showed a clear preference for nesting in heather. Within heather moorland, harriers nested in taller heather (average height 46cm) and nearer streams than expected by chance. More nests were on northwest-facing slopes than expected by chance. We found no evidence that breeding success was influenced by habitat or topography. Heather moorland is declining in the uplands due to overgrazing and afforestation. The association of harriers with heather suggests that their future may become increasingly dependent on moorland, where heather is maintained for grouse.