The key to finding out who poisoned a bird of prey could lie within a "rogue minority" in the racing pigeon community, police said.
A peregrine falcon was found poisoned at Glendinning Quarry in Ashburton, Devon, on Tuesday and died a day later.
Police have described the area as a "hot spot" for suspected poisonings.
The RSPB has offered a £1,000 reward for information which directly leads to the prosecution of the offender.
PC Josh Marshall, Devon and Cornwall Police's wildlife crime officer said: "The answer to solving and preventing these poisonings could lie somewhere within a rogue minority of the racing pigeon community."
Peregrine falcons sometimes eat racing pigeons, which "causes conflict", he said.
The falcon will be forensically examined to establish the cause of death and a police investigation has been launched.
Other incidents in the Ashburton area:
- 2011: One poisoned peregrine falcon at White Cleaves Quarry, Buckfastleigh
- 2005: Racing pigeon used as poisoned bait at Glendinning Quarry, Asburton
- 2005: One poisoned peregrine and one pigeon used as poisoned bait
- 2003: Two men with a pigeon on a length of string appeared to try and lure peregrines from the top of White Cleaves Quarry
- 2000: One poisoned Peregrine at Glendinning Quarry
- 2000: One shot sparrowhawk near Buckfastleigh, which survived
- 1992: Two dead peregrines at White Cleaves Quarry, with pigeon flesh in crop
PC Marshall said: "Generally the method used will be to smear the bait with a Vaseline-type substance containing the poison onto either a live or dead bird."
He warned the poison was also toxic to humans and pets and that people should not touch dead or injured birds.
South West Peregrines, a volunteer group which monitors the birds, has described the incident as "abhorrent".
Tony Whitehead, from the RSPB, said: "Once again, it appears the peregrines at this site have been deliberately targeted and, it is suspected, poisoned.
"Should this prove to be the case, this is outrageous and the criminals must be brought to justice."
The Royal Pigeon Racers Association has been contacted for comment.