Some of Scotland's most vulnerable bird species are in decline because of "poorly positioned" wind turbines, a new study has shown.

The RSPB Scotland study looked at 12 operating upland wind farms in the UK and found that numbers of several birds of high conservation concern are reduced close to the turbines.

Affected birds include the hen harrier and golden plover, which are protected under European law, and the curlew, which is a high-priority species under the UK Biodiversity Action Plan.

The study found that the population density of breeding birds is reduced by between 15 and 53 per cent when nests are within 500 metres of a turbine.

The RSPB called for better planning when wind farms are being considered to take bird populations into account.

James Pearce-Higgins is asenior conservation scientist with RSPB Scotland and lead author of the report.

He said: "There is an urgent need to combat climate change, and renewable energy sources, such as wind farms, will play an important part in this.

"However, it is also important to fully understand the consequences of such development, to ensure that they are properly planned and sited."

Wind farms have two major impacts on bird populations: collisions result in bird strike mortality, notably of raptors, at some sites; disturbance displacement - the fact that birds may use areas close to the turbines less often than expected - also potentially reduces the carrying capacity of an area.

The upland wind farms were surveyed six times during the breeding season for a dozen species: golden plover, lapwing, curlew, snipe, red grouse, buzzard, hen harrier, kestrel, skylark, meadow pipit, stonechat and wheatear.

The distribution of birds across each wind farm was compared with that on similar nearby sites without turbines.

Seven species - buzzard, hen harrier, golden plover, snipe, curlew, wheatear and meadow pipit - were found less often than would be expected close to the turbines.

Andy Douse, ornithological policy and advice manager with Scottish Natural Heritage said: "SNH welcome the publication of this important paper, as it provides us with unequivocal evidence of both the nature and scale of bird displacement at operational wind farms."

The study was funded by RSPB Scotland, the Scottish Government, Scottish Natural Heritage, and the Scottish Mountaineering Trust.