Three red kites that were part of a species re-introduction project have been found poisoned.
One of the birds was part of a pair that had produced 16 chicks since 1999.
The birds were found in central Scotland a month ago but tests have only now confirmed that they were killed with poisoned bait.
Lynn Bowser, of Argaty Red Kites, a feeding project for the birds on a farm north of Stirling, said there was no doubt that they were deliberately poisoned.
She added: “We are very angry about it. These birds are not a threat to anything, that is what is really galling.
“The typical way that one of these birds gets poisoned is that someone will lace a rabbit carcass with poison and lay it out.”
Red kites, common in Scotland 250 years ago, were hunted to extinction and have been the subject of a re-introduction scheme that has resulted in 80 pairs breeding around Scotland.
But according to the RSPB the illegal poisoning of raptors is on the increase, with 42 confirmed incidents last year, compared to 19 the previous year.