A balanced approach to hill farming can play a role in helping the hen harrier, one of Britain's most threatened birds, RSPB Scotland has said.
The organisation said a study had shown the right balance of sheep, livestock and grazing, and support for farmers, was fundamental.
Hen harrier numbers on Orkney fell when sheep numbers increased, and recovered when sheep were then reduced.
The birds are regarded as one of the most persecuted raptors.
Dr Arjun Amar, the senior conservation scientist with RSPB Scotland who led the study, said: "This is a major addition to our understanding of the conservation needs of hen harriers.
"Illegal disturbance and killing continues to be the main barrier to this beautiful bird returning to many parts of the country where it should be commonplace.
"We now know that, where the species is freed from persecution, grazing management can be a pivotal tool in helping hen harrier populations to recover, and may also benefit other species which rely on grassland voles as prey - kestrels, barn owls and short-eared owls, for example."
Vicki Swales, head of land use policy at RSPB Scotland, added: "This study shows the crucial importance of getting the right balance in grazing systems.
"Too many livestock and we lose valuable species; if sheep and livestock and numbers decline too far, this too is likely to cause a decline in the habitat quality, and have profoundly detrimental impacts on hen harriers and other vole-dependent species.
"This is why we need to avoid the broad brush approach of encouraging more livestock everywhere."
The new study is being published in the Journal of Applied Ecology.