Scottish Natural Heritage has defended its controversial decision to allow ravens to be killed for the protection of wading birds.
The licence, for the Strathbraan area of Perth and Kinross, has prompted outrage from conservationists because ravens are a protected species.
But wading birds, such as lapwings and curlews, are in a rapid decline which is "reaching crisis point."
Land managers say the control measures allow all species to thrive.
Gamekeepers say the ravens often arrive in glens in significant numbers where they attack and kill the wading birds.
RSPB Scotland insists there is little evidence that ravens are the main cause of the decline in numbers.
Nick Halfhide, head of sustainable development at Scottish Natural Heritage (SNH), told BBC Scotland: "We really understand that people find this a difficult topic. Killing one species to protect another isn't something that others like, but unfortunately it's something land managers do on a regular basis and they have to do that to protect their interests.
"It's not just private land managers, farmers and gamekeepers, but it's also something that the nature conservation bodies do on a regular basis. And indeed the RSPB itself acknowledges that it kills more hooded crows in a year than we have given a licence for for ravens in this case."
The five-year trial allows land managers to kill up to 69 ravens in the first year but that figure will be reviewed annually.
SNH said that represented less than 0.5% of the total raven numbers in Scotland.
Ronnie Kippen, a gamekeeper involved in the project, said: "They may only be here for less than three or four hours because they will hoover that area as well as any spaniel will hunt a field. They will go back and forward in the wind over that area and that's where the damage is done.
"If RSPB can come up with another answer, and they've been given millions of pounds of public money to do this and the waders are still going down, if they come up with another answer then that's fine," he added.
The decision has prompted an outcry from many conservationists who believe the impact of shooting ravens has not been properly assessed.
'Demonising one bird'
They have questioned the motivations of land managers and suggested the move is about protected red grouse, used for shooting, rather than waders.
Television presenter Chris Packham has written to SNH's chairman saying its reputation lies in "bloodied tatters."
James Reynolds from RSPB Scotland feels the ravens are being incorrectly blamed for waders disappearing.
He said: "[The reasons] are many and varied including farming, forestry and other sorts of land uses.
"All of those things together are having an impact, but certainly demonising one bird for that is, in our view, not supported by any evidence."
SNH has instructed its Scientific Advisory Committee to review the trial but the licence has not been revoked.
RSPB Scotland said that decision was "illogical" and wants it suspended until the committee reports its findings.