Red kites are among the birds which have been killed

Scottish Natural Heritage used aerial photographs to map the areas where a process is carried out to encourage driven red grouse.

It found that these sites, where gamekeepers routinely undertake predator control, accounted for 7.7% of the total upland area in Scotland.

However, between 34% and 54% of all illegal poisoning incidents over the last 19 years have taken place in these areas.

Dr Phil Whitfield, senior ornithologist with SNH, said: "It is obvious that many people have actively chosen to ignore the serious implications that poisoning has for wildlife and public health and safety.

"Our analysis confirms that the use of poison by grouse moor managers is widespread and probably carried out by a large number of people.

Red grouse

"Let us hope that the proposed Nature Conservation Bill can help end this practice."

Scotland's sporting estates have long been blamed for many of the illegal poisonings of birds of prey such as eagles, buzzards and red kites.

Strip muirburn is a habitat where heather is periodically burnt to create a mosaic of short and long heather favoured by red grouse.

The survey suggested that the practice of laying out poisoned baits to kill scavenging or predatory species had become increasingly associated with these areas in the last 20 years.

Sporting estates have been blamed for poisonings

It was thought that illegal poisoning had declined in other upland habitats as farmers, in particular, responded to requests to use only legal methods of control.

The authors of the report said there had been little to suggest that the use of poisoned baits had declined on grouse moors.

Duncan Orr-Ewing, head of land use policy with the Royal Society for the Protection of Birds Scotland, said: "Illegal poisoning of birds of prey is a persistent problem on many upland Scottish sporting estates and there seems to be little willingness by those involved with grouse moor management to tackle this issue.

"This detailed SNH study confirms the extent of the problem."