Rare birds of prey from an award winning reintroduction project have been found poisoned.
Red kites are scavengers which eat already dead animals
Three red kites from the Argaty Red Kite visitor centre near Doune were discovered outside the grounds of the farm a few weeks ago.
Post mortem examinations on the birds have revealed extremely high levels of poison in their systems.
One of the birds killed had fathered 16 red kite chicks since his release into the wild in 1999.
Investigators said the high level of toxin in the bird's system meant the poisonings were unlikely to have been accidental.
A Central Scotland Police wildlife crime officer is investigating the incident.
Lynn Bowser, who runs the Argaty project, said that despite red kites being scavengers which eat already dead animals, they can be targeted by gamekeepers who view all birds of prey as a threat.
She said: "This must have been a deliberate act - there is no other way that such high levels of toxin could be in these birds.
"We are very angry about it.
"These birds are not a threat to anything - that is what is really galling.
"They don't eat anything much other than the carcasses of dead animals."
The deaths are the latest in a spate of poisonings of red kites across Scotland.
Red kites were common in Scotland 250 years ago, but were hunted to extinction.
Reintroduction schemes have resulted in about 80 breeding pairs, with populations now well established in parts of the country.
In July, red kites reintroduced to the Highlands by Harrods boss Mohammed Al Fayed were found poisoned near Tomintoul, Aviemore and Fort Augustus.
The RSPB say such poisoning incidents are on the increase.
James Reynolds of RSPB Scotland described the incident as "shameful".
He said: "The continuing illegal persecution of red kites in Scotland is deplorable, irresponsible and criminal.
"As these shameful incidents at Argaty demonstrate, their impact can spread way beyond persecution of rare protected species, and can damage businesses and other interests in the area."