One of the 30 red kite chicks sent to Ireland in a project to reintroduce the species there has been found shot dead.
The chicks are among the first of around 120 birds planned for release
The kite was among a batch taken from Powys to the mountains of County Wicklow six weeks ago.
Police in Ireland are investigating after it was found with seven shotgun pellets.
Tony Cross of the Welsh Kite Trust in Rhayader, who worked on the scheme, said the shooting was a setback but did not "invalidate" the plan.
The chicks were released six weeks ago in the first stage of a four-year programme to bring back a bird persecuted to extinction in Ireland.
"I'm disappointed one has been shot so early," Mr Cross said.
"It's a bit of a set back but it doesn't invalidate the project with the other 29 birds out there.
"It is particularly worrying that this illegal persecution has taken place in an area currently frequented by several other of the released kites as it potentially puts them at similar risk.
X-ray of the bird showing seven shotgun pellets in white
He added: "It would be a tremendous pity if the illegal and selfish acts of a few cast a shadow over the great work being done."
The bird was found dead on 28 August in a farm field north of Arklow.
The progress of the other chicks is being tracked by tiny radio transmitters attached to their distinctive fork tails.
Mr Cross said he thought contact had been made with all, bar three, of the existing birds.
They are the first of around 120 birds planned for release over the next five years.
The Golden Eagle Trust of Ireland, which spent two year setting up the project, said it was very worrying.
The trust said landowners in Wicklow had in general supported the reintroduction of the kite, which is protected under European law.
Mr Cross said he was not surprised one of the birds had been shot as the area had been devoid of birds of prey for a few hundred years.
Damien Clarke, of the Golden Eagle Trust, said the kites from Wales would have been the closest relative to the birds driven to extinction there decades ago.
Once-widespread, kites were persecuted to near extinction in England and Scotland by 1879.
A small number of kites managed to survive in the remote uplands of mid Wales.
During the past 15 years a project to re-introduce kites throughout the UK has proved successful.