Monitoring the Exposure of Barn Owls to Second-Generation Rodenticides in Southern Eire

✍ Scribed by Eadsforth, Charles V.; Gray, Alan; Harrison, Elizabeth G.

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 741 KB
• Volume: 47
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199607)47:3<225::aid-ps407>3.0.co;2-p

✦ Synopsis

In an extensive field study conducted over five counties in southern Eire during the winter of 1988-89, 19 Barn Owl (Tyto alba) roosts and/or nests were located. The local farmers and landowners within about a one-mile radius of the Barn Owl sites were surveyed concerning their use of rodenticides and observations of any secondary rodenticide toxicity effects. Regurgitated owl pellets were collected: (a) for dissection and prey analysis, and (b) for chemical analysis to determine residues of the second-generation rodenticides, brodifacoum, difenacoum and flocoumafen.

Most farmers interviewed used rodenticide baits (73%), and almost all (92%) stated that they took precautions to protect domestic and wild non-target animals. The four rodent species, brown rat, wood mouse, house mouse and bank vole provided 83% of the Barn Owl diet, and birds contributed another 12%. At least 97% of the 89 pellets analysed contained less than the limit of determination of the three second-generation rodenticides, 0.01-0-02 mg kg-' of each isomer. Apparent residues in the remainder were likely to be the result of interference from co-extracted material. These results indicated that during the monitoring period, none of the owls studied was exposed to significant residues of these rodenticides in their prey.