Farmers that use rodenticide are being urged to follow the product's label instructions after two thirds of barn owls have been found to contain the chemical.
Barn owls are being found with detectable liver residues of two or more second generation anticoagulant rodenticides (SGARs).
Another 21 per cent were positive for one SGAR in this Campaign for Responsible Rodenticide Use (CRRU) surveillance.
The highest frequency detections were of bromadiolone, difenacoum and brodifacoum.
For the first time in four years, one specimen was identified in which SGAR exposure was a possible contributor to the cause of death.
Of 100-a-year analysed, the other 399 had died mainly from either road traffic trauma or starvation.
Compared with a 2006 to 2012 benchmark, these latest results show no significant rise nor fall in total SGAR residues.
Even so, the results come at a sensitive time, according to CRRU chairman Dr Alan Buckle, as the stewardship regime will be reviewed formally by its HSE-led Government Oversight Group during the next two to three months.
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