Wildlife services in west Cork and south Kerry have recovered the bodies of two white-tailed sea eagles.
It has been confirmed that one of the birds was poisoned, while the second bird is also believed to have been poisoned.
White-tailed sea eagles are a protected species under law and are part of a re-introduction programme in which 100 birds have been released in Killarney National Park between 2007 and 2011.
The bird which was poisoned was a female and was released in Killarney in August 2010.
She spent much of last year in south Kerry before moving to the Beara Peninsula between Adrigole and Glengarriff in west Cork last December.
The birds are fitted with electronic tracking devices.
The bird was discovered washed up at the water's edge near Glengarriff a fortnight ago and post mortem results from the State Laboratory at Celbridge show it was poisoned.
It is believed the bird died as a result of eating carrion.
A second dead bird was found at Derrynane in south Kerry earlier this week.
The cause of death is not yet known in this case, but it is also believed to be poisoning.
Project Manager Dr Allan Mee of the White-tailed Eagle Reintroduction Programme expressed his disappointment.
He pointed out that the practice of laying out poison to control crows and foxes is illegal.
Twenty-six eagles have been recovered dead since the reintroduction programme was initiated, with 12 of those confirmed poisoned.