Anticoagulant Rodenticides in Three Owl Species from Western Canada, 1988–2003

Abstract

Anticoagulant rodenticides are widely used to control rodent infestations. Previous studies have shown that nontarget organisms, such as birds, are at risk for both primary and secondary poisoning. This paper presents rodenticide residue information on the livers from 164 strigiformes which included barn owls (Tyto alba), barred owls (Strix varia), and great horned owls (Bubo virginianus), collected from 1988 to 2003 in the province of British Columbia and the Yukon Territory, Canada. Livers were analyzed for brodifacoum, bromadiolone, chlorophacinone, diphacinone, difethialone, and warfarin. Our results show that, of the 164 owl livers analyzed, 70% had residues of at least one rodenticide, and of these 41% had more than one rodenticide detected. Of the three species of owls examined, barred owls were most frequently exposed (92%, n = 23); brodifacoum and bromadiolone were most often detected, with liver concentrations ranging from 0.001 to 0.927 mg/kg brodifacoum, and 0.002 to 1.012 mg/kg bromadiolone. Six of the owls (three barred owls, two barn owls, and one great horned owl) were diagnosed as having died from anticoagulant poisoning; all six owls had brodifacoum residues in the liver.

Second generation anticoagulant rodenticides in predatory birds: Probabilistic characterisation of toxic liver concentrations and implications for predatory bird populations in Canada

“…Diamond in the center of the box represents average, line is the median, box is the upper and lower quartiles and the whiskers are the standard deviation. Sources of the data are: Newton et al 1990Newton et al , 1998Newton et al , 2000Stone et al 1999Stone et al , 2003Albert et al 2010; EIIS 2010 download.…”

“…In an attempt to monitor exposure in non-target wildlife, the presence 22 of detectable SGAR residues as well as the magnitude of concentrations has been 23 measured in the livers of some Canadian, American and European predatory birds and 3 24 scavengers (Albert et al 2010, Newton et al 1990.…”

“…85 Using these equations, liver residue levels (in mg/kg wet weight (ww)) were determined Albert et al (2010). 50 mg of 114 liver was ground in a mortar with about 5 g anhydrous sodium sulphate (Fisher no.…”

“…Data 162 published by Newton et al (1990Newton et al ( , 1998Newton et al ( , 2000n=45), Albert et al (2010;n=164) …”

“…The widespread exposure in Canada in part most likely reflects the increase in sales 330 and use of SGARs in the last few decades (Albert et al 2010), and the use of persistent 331 compounds that remain detectable in the liver long after the exposure event (Laas et al 332 1985). However, it is also clear from our data that multiple exposures, as detected by the …”