Four red kites have been killed this year
Birds of prey are under greater threat from poisoning and shooting than from egg thieves, according to wildlife experts.
Police and conservation bodies in north-east Scotland have launched their annual campaign to protect birds of prey, while they hatch eggs and raise chicks.
It is the first nesting season that wildlife criminals north of the border have faced possible jail sentences after the law was amended to bring penalties into line with England.
However, there are fears that an emphasis on catching egg thieves mean other - even more serious - cases are being ignored.
The RSPB has said that no egg thieves were sighted and no nests were reported disturbed in Scotland during this year's spring breeding season.
Police said this was down to greater public awareness and tougher sentencing options for Scottish courts.
Despite the success of operations to keep watch on nests where vulnerable birds are raising their chicks, wildlife experts are worried.
Gamekeepers and pigeon fanciers have been accused of killing birds of prey, but their activities are hard to detect.
Jane Molloy, a licensed volunteer from the North East Raptor Study Group, said: "I would think the biggest threat is likely to be persecution.
"Somebody who does not want them here for one reason or another.
Keepers operate on their own in a remote environment and that is very difficult to detect.
Scottish Natural Heritage
"In this area, we don't really have bother with people trying to steal the eggs."
Five red kites and a rare sea eagle have been deliberately killed in Scotland already this year.
Four of the kites were poisoned with an unapproved pesticide and the fifth was shot.
RSPB Scotland said there were only 53 breeding pairs of red kites north of the border.
John Hardie from the North East Raptor Study Group, said: "The Peregrine Falcon population in the North East, on grouse moors, has declined by about 40% over the past six or seven years.
Difficult to detect
"Our Hen Harrier population in the North East could very easily become extinct in a few years."
He said that he had no doubt that this decline was down to estates and gamekeepers deliberately killing the birds.
Paul Timms, from Scottish Natural Heritage, said that there were problems getting convictions for people killing birds of prey.
He said: "The problem, and this is actually a police matter, is getting enough evidence.
"Keepers operate on their own in a remote environment and that is very difficult to detect."