Police have issued a reward for information after a Red Kite was poisoned in Tadcaster.
A member of the public found the bird at Toulston Polo Ground in October 2012 but tests have recently revealed it died from the illegal poison Carbofuran, which was banned in 2001.
The Red Kite was born in Wales in 2009 and is believed to be one of a breeding pair, which first bred at Tadcaster Grammar School in 2012.
They are the first known Welsh-born Red Kites to have bred in Yorkshire.
Police and the RSPB have offered £1,000 reward for anyone who can provide information to help catch the culprits.
PC Sarah Ward, of Tadcaster safer neighbourhood team, said: “This crime is appalling.
“The use of Carbofuran is both unlawful and highly dangerous.
“It is toxic and a few granules could kill.”
Doug Simpson, Yorkshire Red Kites co-ordinator, said: “The loss of any bird through illegal poisoning is a big disappointment. It is particularly disappointing in this case, with this kite being of Welsh origin and the first from that source known to have bred in Yorkshire.”
Anyone with information should contact Tadcaster police on 101, the RSPB on 0845 4663636 or Crimestoppers on 0800 555111.