Police believe protected peregrine falcons which went missing in the Ballymena area of Co Antrim earlier this month may have been shot dead.
After two adult falcons and two chicks of the protected species disappeared from the Glenwherry area, one chick was found fatally injured.
It is thought the other three falcons were killed.
The two adult falcons were being watched over recent months in the nest and one of the chicks which had only recently flown from the nest was found dead below the cliff, said the Northern Ireland Raptor Study Group.
Group chairman Jim Wells said: "Every summer it is the same - illegally poisoned or shot falcons. This has to stop.
"It is an absolute disgrace that anyone thinks they have justification for shooting a rare and specially protected bird."