Anticoagulant rodenticide exposure in common buzzards: Impact of new rules for rodenticide use.

Rodenticides are a key component of rodent management strategies, but birds of prey are susceptible to non-target exposure. New rules on sale and use of rodenticide products were introduced across the UK in 2016 in an industry-led stewardship scheme, with the aim of reducing this risk. To determine if this intervention has achieved its aim, exposure to second generation anticoagulant rodenticides (SGARs) was measured in buzzards. Liver samples from 790 buzzards collected between 2005 and 2022 (excluding 2016 and 2017 samples) were analyzed and the percentage presence and concentrations of SGARs from pre-stewardship and post-stewardship samples were compared. There was no statistically significant decrease in the percentage of buzzards exposed to bromadiolone, difenacoum or combined SGAR residues after the introduction of stewardship. The percentage of buzzards exposed to brodifacoum increased significantly post-stewardship, from 8 % to 27 %. There were no significant decreases in the concentrations of individual SGARs post-stewardship but concentration of combined SGARs increased significantly post-stewardship. Individual buzzards were significantly more likely to be exposed to multiple SGARs post-stewardship. Rodenticide poisoning was recorded as the cause of death for 5 % of pre- and post-stewardship buzzards with detectable levels of SGARs, and 90 % of these had combined SGAR residues >0.1 mg/kg. These findings suggest that the industry-led stewardship scheme has not yet had the intended impact of reducing SGAR exposure in non-target wildlife. The study highlights a substantial increase in exposure of buzzards to brodifacoum and to multiple SGARs post-stewardship, indicating that further changes to the stewardship scheme may be necessary.