The group which monitors peregrine falcons in NI has said it is concerned about the bird's future following a series of deaths this year.
The Northern Ireland Raptor Study Group (NIRSG) said 2010 has been one of the worst years for "peregrine persecution".
Four birds have been killed in suspicious circumstances, so far this year.
The NIRSG has appealed to those who are behind the attacks to stop.
In July, a young peregrine was found dead in a County Londonderry quarry.
Toxicology tests confirmed it had been poisoned with the banned substance alphachloralose.
Another adult male was found in a poor condition and close to death.
The NIRSG said an adult female and another chick were missing from the same quarry and have never been located.
Three other peregrines have been found dead in Northern Ireland. Two were found within a month of each other in the same location at Belfast Harbour.
A third was found shot in Portaferry, County Down.
It had to be put down by a vet after shotgun pellets were discovered in its wings.
In March, a pigeon covered in poison with a piece of string attached to its leg was found flying around a quarry in County Antrim on a Monday morning.
Quarries have become an adopted habitat for many peregrine falcons who now live inland.
Their preferred habitat is coastal areas.
The pigeon was shot by police to prevent it from escaping to two nearby primary schools and to prevent it from being eaten by a peregrine falcon.
Laverne Bell from the Quarry Products Association (QPA) which represents the quarry industry condemned the incident.
"The quarrying industry has a close affiliation with this amazing bird and we condemn any acts of persecution against peregrines, or any other birds of prey."
NIRSG monitoring results have shown a 20% decline in the number of breeding pairs of peregrine in Northern Ireland in less than 20 years and the number of young successfully fledging has declined by 35%.
The group says at least 50% of raptors (birds of prey) die naturally within their first year of life.
External factors such as deliberate killing through shooting and/or poisoning will add to this natural mortality and may cause a population decline.
The NIRSG said the peregrine population could not continue to withstand the consistent, targeted and apparently co-ordinated approach to peregrine persecution in Northern Ireland and urged whoever is doing this to stop.
Emma Meredith, Wildlife Liaison Officer for the PSNI said "such acts cannot and will not be tolerated".
"We urge anyone that has any information about peregrine persecution or wildlife crime to report it directly to the police or anonymously through Crimestoppers on 0800 555 111 to assist us in bringing these criminals to justice."