Published Tuesday, 20 August 2013
The bird was discovered in the Castlewellan area of Co Down last Wednesday.
It was the fourth red kite to be found dead this year, which the RSPB said represented 30% of the breeding population in the province.
A post-mortem is due to be carried out by the Agri-Food and Biosciences Institute.
The charity is appealing for the public's help in uncovering the cause of the deaths, although it is strongly suspected that it, and the other birds, were poisoned.
Red kites were once common in Ireland but were persecuted to extinction in the 18th century.
In 2008, the RSPB began a reintroduction project that has been successful in encouraging the birds to breed.
There were only 10 breeding pairs in Northern Ireland. The four deaths to date consisted of two breeding males, one breeding female and a juvenile.
The female was found dead in the nest where she was incubating two eggs, meaning the chicks inside also perished.
Adam McClure, Red Kite Officer for the RSPB, said: "All birds of prey are protected under the law, but unfortunately this doesn't always mean that they are safe from poison.
"In some cases, they are deliberately targeted as some people incorrectly see them as a threat to their live stock or game birds.
"They may also ingest the poison by eating dead mice or rats that have been killed by rodenticides."
Emma Meredith, PSNI wildlife liaison officer, added: "Police take wildlife crime seriously and if it is found that there is a breach in the legislation then they will investigate.
"Anyone who suspects a crime and/or has information about the deaths of the birds is asked to contact the Police Service of Northern Ireland on 0845 600 8000 or anonymously through Crimestoppers on 0800 555 111."
© UTV News