Hen Harrier Translocation as a Conservation Tool in the United Kingdom- a Feasability Study.

Abstract

1. The objective of this study was to assess the feasibility of translocating hen harriers in the UK in order to help reduce the impact of their predation on grouse moors and enhance their range and abundance.
2. A review of recent literature on hen harrier ecology suggested that hen harriers would be a suitable subject for translocation, despite the variability in the pattern of dispersal shown from studies in Scotland. Translocation over a long distance from the donor site would have the most beneficial effect for conservation. However, translocation on its own would not be a suitable method of reducing harrier predation impact on grouse.
3. Results from an ongoing project in France demonstrated that hen harriers could be reared easily in captivity and released back to the wild successfully. Further, some of the birds were re-sighted in the release area the following year. Comparison of re-sighting rates of Montagu's harrier with data on hen harrier from other studies suggested that hen harrier exhibits sufficient philopatry necessary for successful translocation.
4. Modelling simulations based on the best available data suggested that:
a) By limiting the number of nesting female harriers, predation impact could be reduced to a level allowing viable driven grouse shooting.
b) Taking half the harrier eggs from each clutch for captive rearing to provide stock for translocation could reduce predation impact only to a limited extent.
5. Assessments of habitat and food availability suggested that some upland areas in Wales and south-west England and some lowland areas in southern England may be suitable recipient sites for translocated birds. A range of other factors important for successful re-introduction were also considered.
6. IUCN guidelines are fulfilled for a translocation to sites free from illegal control, which are beyond the dispersal distances of the existing population. This suggests that translocation to sites in southern and south-western England may have the most conservation value.
7. It was concluded that hen harrier translocation was feasible, in terms of enhancing harrier range and abundance, but on its own would not provide an effective method of controlling harrier densities on grouse moors. The value of executing a costly and risky translocation programme was doubtful, so long as the problem of illegal control on grouse moors remained. The search for a solution to this core problem emerges as the current priority. However, establishing new hen harrier population foci beyond the reach of illegal control may become highly desirable if other initiatives are not successful.