The volunteer group supporting the re-introduction of white-tailed sea eagles in Mountshannon, Co Clare, has announced the death of a female bird of that species known as Saoirse.
"Toxicology reports confirmed avian influenza (bird flu) as the cause of death," the group said on its Facebook page.
The Department of Agriculture has not yet confirmed whether this bird died of the deadly H5N6 strain of the virus, which killed another white-tailed sea eagle in Co Tipperary in January.
The H5N6 strain has been spreading in wild birds in mainland Europe and Britain, and infected one farm in the Netherlands last month.
A second case of the virus was confirmed in Ireland on Friday when a wild buzzard tested positive after being found dead on the Tipperary shore of Lough Derg.
All keepers of birds must register with the Department of Agriculture. Poultry farmers and owners of backyard flocks are encouraged to keep farmed and wild birds segregated with netting and separate feed and water supplies. Different species of farmed birds should also be kept separate, especially ducks and geese.
If you come across dead or sick birds, do not touch them and report them to the Department of Agriculture's avian influenza hotline on 076-106 4403 during normal office hours or 1850-200 456 outside of normal office hours.
Full coverage: bird flu