The National Parks and Wildlife Service is appealing for information after a peregrine falcon was found dead in Dalkey Quarry in Dublin.
The discovery on Saturday came just days after a pair of falcons was reported to be nesting in the area.
A post-mortem examination is being carried out to determine the cause of the bird's death.
The NPWS says while it is possible that the peregrine was poisoned, disturbance of wildlife by drones is also causing problems.
In 2014 a pair of falcons nesting in the quarry was targeted after someone left two tethered pigeons laced with poison for them to eat.
Peregrine falcons are protected under European and national legislation.
The NPWS says the bird's death will almost certainly result in the failure of the eggs in the nest to hatch.