Since 1983, investigations have been made into the exposure to and effects of the second generation of anticoagulant rodenticides (SGARs) on barn owls and more recently kestrels and red kites have been added to the species monitored.
Data on long-term trends have been adjusted to account for changes over time in sensitivity of analytical methods. This has meant that very low residues (<0.025μg/g wet weight), which are now easily detectable, are not included in the time trend analysis.
The proportion of owls with detectable SGAR residues was found to be two-fold higher in England than in either Scotland or Wales. Overall, the proportion of barn owls with detectable liver concentrations of one or more SGAR has increased significantly over the course of monitoring.