There has been an ongoing research project on the subject of birds of prey, especially hen harriers, and red grouse at Langholm moor in southern Scotland for a number of years now. The end point of this project is to re-establish sufficient numbers of red grouse so that the moor can once again be shot over and have a resident population of hen harriers on the moor. One of the main features is to provide food for the harriers so that they do not prey on the grouse.
The results have been controversial since so many differing groups have a direct and/or indirect interest.
http://www.langholmproject.com/http://tinyurl.com/o67dvbm