The PSNI are asking anyone who has information about how a trio of birds came to be poisoned to step forward.
All of the deaths took place in Co Antrim, with the first being on March 15 at a forest in the Glenarm area.
On that occasion the creature – a buzzard – was found to have suffered poisoning via a substance known as carbofuran.
Another buzzard was reported dead on March 29, also near Glenarm, and tests showed it was exposed to alpha chloralose.
Then on April 11 at a quarry on the Glenhead Road, Ballymena, a peregrine falcon was found dead. It was due to carbofuran.
At the same quarry in 2012, another peregrine falcon had been found shot dead.
The PSNI said “we would have particular concern over any poison, but particularly over carbofuran”, which they said the substance could kill a child or a pet if it came into contact with it.
Anyone killing a bird of prey could go to jail, and possibly face a fine of up to £5,000.
Anyone with information can call police on 101 or Crimestoppers on 0800 555 111.