The birds had been among 100 released in Killarney National Park as part of a reintroduction programme between 2007 and 2011.
So far, 26 have died, including 12 from illegal poisoning.
An autopsy on the female found washed up on the seashore near Glengarriff on Jan 18 confirmed poisoning, believed to be from eating carrion.
The bird was released in Aug 2010 and spent much of 2012 in south Kerry before moving to the Beara peninsula, in December.
Earlier in the week, another female eagle was found dead in Derrynane, but it has not been possible to determine the cause of death.
Arts, Heritage and the Gaeltacht Minister Jimmy Deenihan said the poisoning was ‘’very serious,’’ adding his department was assisting investigating gardaí.
White-tailed Eagle Reintroduction project manager Dr Allan Mee said illegal poisoning continued to be a problem, with two birds lost to poisoning in Mayo and Donegal last year.
“Over the last few years, we feel we have made good progress in tackling the poisoning problem in Kerry, with the co-operation of the farming organisations and Teagasc, so we are disappointed to lose another bird to poisoning,’’ he said.
“We realise that landowners have in the past used poison to control crows and foxes, especially around lambing time. However, we would like to remind people that use of poisons or other substances for the control of foxes and crows is now illegal.’’
With the co-operation of farming organisations, an advice leaflet was distributed to all sheep farmers in West Cork and south Kerry in 2011 and 2011.
Last year, white-tailedeagles nested in Ireland for the first time in over 100 years and a pair laid eggs in Lough Derg, Co Clare. And, though these eggs failed to hatch, hopes are high that 2013 will be the breakthrough year.
“We know of six pairs that could build nests and breed in 2013, including four pairs in Kerry, one in Clare and one in Galway,” Dr Mee said, adding they hoped to establish a small but viable breeding population.
“As we are no longer releasing birds into the wild, it is vital that we now start producing our own chicks in the wild to replace any birds that are lost and maintain the population. We are hoping that this year will be a milestone.”