Barn owl numbers have been falling

Last week's search was prompted by the earlier discovery of six dead buzzards in the area by members of the public.

The investigation found the bodies of five barns owls, a tawny owl, two buzzards and a kestrel. It is not yet known how the birds died.

RSPB Scotland said: "Cases like this highlight the very real and continuing threat to our birds of prey."

The search was carried out by officers from RSPB Scotland, Lothian and Borders Police, the Scottish SPCA and the Scottish Executive Environment and Rural Affairs Department (SEERAD).

Post mortem examinations will now be carried out on the bodies.

Barn owls have suffered a serious decline in numbers over the last few decades, mainly due to loss of nesting sites.

The Royal Society for the Protection of Birds said that four of the six buzzards found earlier had been poisoned.

RSPB Scotland's Dave Dick said the society was increasingly working with police forces and other groups on investigations.

The body of one kestrel was found

"With our combined knowledge and improved legislation, more wildlife criminals are being caught and dealt with by Scottish courts," he said.

"Cases like this highlight the very real and continuing threat to our birds of prey."

The Scottish Landowners' Federation said it did not in any way condone illegal persecution of wildlife.

A spokesperson said that only concerted action would defeat criminal acts which harm Scotland's natural heritage.

Constable Mark Rafferty, wildlife crime officer for Lothian and Borders Police, said: "Persecution of any wildlife, in particular birds of prey, is a very serious threat and will be investigated by all relevant organisations.