Second generation anticoagulant rodenticide residues in barn owls 2018

The current report is the fourth in a series of annual reports that describe the monitoring of second generation anticoagulant rodenticide (SGAR) liver residues in barn owls Tyto alba in Britain. This work is an element of an overarching monitoring programme undertaken to track the outcomes of stewardship activities associated with the use of anticoagulant rodenticides. The barn owl is used for exposure monitoring as it is considered a sentinel for species that are generalist predators of small mammals in rural areas. The specific work reported here is the measurement of liver SGAR residues in 100 barn owls that died in 2018 in locations across Britain. The residue data are compared with those from 395 barn owls that died between 2006 and 2012 (hereafter termed baseline years), prior to changes in anticoagulant rodenticide (AR) authorisations and onset of stewardship. As in the baseline years, the compounds detected most frequently in barn owls that died in 2018 were bromadiolone, difenacoum and brodifacoum. Overall, 87% of the owls had detectable liver residues of one or more SGAR. The metrics to be used for stewardship monitoring are reported below in terms of differences between owls that died in 2018 and in baseline years. Numbers of barn owls containing detectable residues of flocoumafen and difethialone. There was no significant difference in the proportion of barn owls with detectable liver residues of flocoumafen between the baseline years and 2018. There was a significantly higher proportion of barn owls with detectable liver residues of difethialone in 2018 compared to baseline years (8% vs 0.3% ). The ratio of birds with ”low” (100 ng/g wet wt.) concentrations for any single SGAR or for ∑SGARs. There was no significant difference between barn owls from baseline years and from 2018 for any individual compound or for summed SGARs (∑SGARs), although a decrease in the proportion of birds with “high” difenacoum residues approached significance. Average concentrations of brodifacoum, difenacoum, bromadiolone and ∑SGARs in the cohort of owls with “low” residues (100 ng/g ww). There was no significant difference between barn owls from baseline years and from 2018 in the concentrations of either “low” or “high” residues for bromadiolone, difenacoum (data tested statistically only for “low residues”), all residues summed (∑SGARs), or “high” brodifacoum residues. The median concentration of “low” brodifacoum residues was higher in birds from 2018 than in baseline years. Overall, there were few differences in liver SGAR accumulation between barn owls that died in baseline years and in 2018. The lack of significant reductions in SGAR residues in barn owls in 2018 suggests that full implementation of stewardship since 2016 has yet to result in a reduction in exposure of barn owls to SGARs

Second generation anticoagulant rodenticide residues in barn owls 2015

CEH contract report to the Campaign for Responsible Rodenticide Use (CRRU) UK

Second generation anticoagulant rodenticide residues in barn owls 2016

CEH contract report to the Campaign for Responsible Rodenticide Use (CRRU) UK

Second generation anticoagulant rodenticide residues in barn owls 2019

The fifth in a series of annual reports describing the magnitude of second generation anticoagulant rodenticide (SGAR) liver residues in barn owls Tyto alba in Britain

Second generation anticoagulant rodenticide residues in barn owls 2020

The current report is the sixth in a series of annual reports that describe the monitoring of second generation anticoagulant rodenticide (SGAR) liver residues in barn owls Tyto alba in Britain. This work is an element of an overarching monitoring programme undertaken to track the outcomes of stewardship activities associated with the use of anticoagulant rodenticides. The barn owl is used for exposure monitoring as it is considered a sentinel for species that are generalist predators of small mammals in rural areas. The specific work reported here is the measurement of liver SGAR residues in 100 barn owls that died in 2020 at locations across Britain. The residue data are compared with those from 395 barn owls that died between 2006 and 2012 (hereafter termed baseline years), prior to changes in anticoagulant rodenticide (AR) authorisations and onset of stewardship. As in the baseline years, the compounds detected most frequently in barn owls that died in 2020 were brodifacoum, bromadiolone, and difenacoum. Overall, 88% of the owls had detectable liver residues of one or more SGAR. Numbers of barn owls containing detectable residues of flocoumafen and difethialone. There was no significant difference in the proportion of barn owls with detectable liver residues of flocoumafen between the baseline years and 2020. There was a significantly higher proportion of barn owls with detectable liver residues of difethialone in 2020 compared to baseline years (5% vs 0.3%) but it was lower than in some of the intervening years (2016-2019). The ratio of birds with “low” (100 ng/g wet wt.) concentrations for any single SGAR or for ∑SGARs. There were significantly higher proportion of birds from 2020 with “high” concentrations of brodifacoum and summed SGARs (ƩSGARs) detected in their livers compared to baseline years. Average concentrations of brodifacoum, difenacoum, bromadiolone and ∑SGARs in the cohort of owls with “low” residues (100 ng/g wet wt.). There was no significant difference between barn owls from baseline years and from 2020 in the concentrations of either “low” or “high” residues for all residues summed (∑SGARs), bromadiolone and difenacoum, or “high” brodifacoum residues. The median concentration of “low” brodifacoum residues was higher in birds from 2020 than in baseline years. Overall, there were few differences in liver SGAR accumulation between barn owls that died in baseline years and in 2020, the eception being a potential increase brodifacoum residues. The lack of significant reductions in SGAR residues in barn owls in 2020 suggests that full implementation of stewardship since 2018 has yet to result in a statistically significant reduction in exposure of barn owls to SGARs

Second generation anticoagulant rodenticide residues in barn owls 2017

CEH contract report to the Campaign for Responsible Rodenticide Use (CRRU) UK. A wide range of avian and mammalian predators and scavengers in rural Britain is known to be exposed to Second Generation Anticoagulant Rodenticides (SGARs). The barn owl Tyto alba is a sentinel for species that are generalist predators of small mammals in rural areas in the UK and monitoring of liver SGAR residues in barn owls has been adopted as an element of the monitoring undertaken as part of anticoagulant rodenticide stewardship. Monitoring of liver SGAR residues in some 100 barn owls per year is conducted in support of stewardship and annually collected data are compared with those from 395 barn owls that died between 2006 and 2012 (hereafter termed baseline years), prior to the 2016 changes in anticoagulant rodenticide (AR) authorisations and onset of stewardship. The rationale for using data on SGAR residues in barn owls that died between 2006 and 2012 as a baseline was that all measurements had been made using the same analytical techniques, there had been little clear change in exposure over that time period, and the data were the most recent available. The aim of the current study was to measure SGAR exposure in barn owls in 2017. As in the baseline years, the compounds detected most frequently in barn owls that died in 2017 were bromadiolone, difenacoum and brodifacoum. Overall, 90% of the owls had detectable liver residues of one or more SGAR. The metrics to be used for stewardship monitoring are reported below in terms of differences between owls that died in 2017 and in baseline years. Numbers of barn owls containing detectable residues of flocoumafen and difethialone. There was no significant difference in the proportion of barn owls with detectable liver residues of either flocoumafen or difethialone between the baseline years and 2017. The ratio of birds with ”low” (100 ng/g wet wt.) concentrations for any single SGAR or for ∑SGARs. There was no significant difference between barn owls from baseline years and from 2017 for any individual compound or for summed SGARs (∑SGARs) Average concentrations of brodifacoum, difenacoum, bromadiolone and ∑SGARs in the cohort of owls with “low” residues (100 ng/g wet wt.). There was no significant difference between barn owls from baseline years and from 2017 in the concentrations of either “low” or “high” residues for bromadiolone, difenacoum and brodifacoum, or for all residues summed (∑SGARs). Although not statistically significant, the median and 75th percentile values of “low residues” of most compounds and ∑SGARs were lower in 2017 [and 2016] than in the baseline years Overall, the lack of statistically significant differences in SGAR accumulation by barn owls in 2017 compared within baseline years suggests that full implementation of stewardship since 2016 has yet to be reflected by a detectable general reduction in exposure of barn owls

Second generation anticoagulant rodenticide residues in barn owls 2021

The current report is the seventh in a series of annual reports that describe the monitoring of second-generation anticoagulant rodenticide (SGAR) liver residues in barn owls Tyto alba in Britain. This work is an element of an overarching monitoring programme undertaken to track the outcomes of stewardship activities associated with the use of anticoagulant rodenticides. The barn owl is used for exposure monitoring as it is considered a sentinel for species that are generalist predators of small mammals in rural areas. The specific work reported here is the measurement of liver SGAR residues in 100 barn owls that died in 2021 at locations across Britain. The residue data are compared with those from 395 barn owls that died between 2006 and 2012 (hereafter termed baseline years), prior to changes in anticoagulant rodenticide (AR) authorisations and onset of stewardship. As in the baseline years, the compounds detected most frequently in barn owls that died in 2021 were brodifacoum, bromadiolone, and difenacoum. Overall, 79% of the owls had detectable liver residues of one or more SGAR. Numbers of barn owls containing detectable residues of flocoumafen and difethialone. There was no significant difference in the proportion of barn owls with detectable liver residues of flocoumafen between the baseline years and 2021. There was a significantly higher proportion of barn owls with detectable liver residues of difethialone in 2021 compared to baseline years (6% vs 0.3%), but it was lower than in some of the intervening years (2016-2019). The ratio of birds with “low” (100 ng/g wet wt.) concentrations for any single SGAR or for ΣSGARs. There were significantly higher proportion of birds from 2021 with “high” concentrations of brodifacoum and summed SGARs (ƩSGARs) detected in their livers compared to baseline years. Average concentrations of brodifacoum, difenacoum, bromadiolone and ΣSGARs in the cohort of owls with “low” residues (100 ng/g wet wt.). There was no significant difference between barn owls from baseline years and from 2021 in the concentrations of “high” residues for all SGAR residues, including ΣSGARs. In contrast, “low” bromadiolone and difenacoum residues were significantly lower in 2021 than baseline years, while “low” brodifacoum residues were significantly higher in 2021 than baseline years. Overall, there were significant differences in liver SGAR accumulation between barn owls that died in baseline years and in 2021: a potential reduction of bromadiolone and difenacoum and an increase of brodifacoum residues from 2016. However, the lack of significant reductions in sum of SGAR residues in barn owls in 2021 suggests that full implementation of stewardship since 2018 has yet to result in a statistically significant reduction in exposure of barn owls to SGARs

Second generation anticoagulant rodenticide residues in barn owls 2022

The current report is the eighth in a series of annual reports that describe the monitoring of second-generation anticoagulant rodenticide (SGAR) liver residues in barn owls Tyto alba in Britain. This work is an element of an overarching monitoring programme undertaken to track the outcomes of stewardship activities associated with the use of anticoagulant rodenticides. The barn owl is used for exposure monitoring as it is considered a sentinel for species that are generalist predators of small mammals in rural areas. The specific work reported here is the measurement of liver SGAR residues in 88 barn owls that died in 2022 at locations across Britain. The residue data are compared with those from 395 barn owls that died between 2006 and 2012 (hereafter termed baseline years), prior to changes in anticoagulant rodenticide (AR) authorisations and onset of stewardship in 2016. As in the baseline years, the compounds detected most frequently in barn owls that died in 2022 were brodifacoum, bromadiolone, and difenacoum. Overall, 79.5% of the owls had detectable liver residues of one or more SGAR. Numbers of barn owls containing detectable residues of flocoumafen and difethialone. There was no significant difference in the proportion of barn owls with detectable liver residues of flocoumafen between 2022 and the baseline years (3% vs 0%). In contrast, there was a significantly higher proportion of barn owls with detectable liver residues of difethialone in 2022 compared to baseline years (6.8% vs 0.3%), but this proportion was lower than in some of the intervening years (2016-2021). The ratio of birds with “low” (100 ng/g wet wt.) concentrations for any single SGAR or for summed SGARs (ΣSGARs). There was a significantly higher proportion of birds with “high” concentrations of brodifacoum detected in their livers in 2022 than in the baseline years. Average concentrations of brodifacoum, difenacoum, bromadiolone and ΣSGARs in the cohort of owls with “low” residues (100 ng/g wet wt.). There was no significant difference between barn owls from baseline years and from 2022 in the concentrations of “high” residues for all SGAR residues, including ΣSGARs. In contrast, “low” bromadiolone and difenacoum residues were significantly lower in birds from 2022 than in the baseline years, while “low” brodifacoum residues were significantly higher in birds from 2022 than in the baseline years. Overall, there were significant differences in liver SGAR accumulation between barn owls that died in baseline years and in 2022: significant reductions of bromadiolone and difenacoum and an increase in brodifacoum residues from 2016. However, the lack of significant reductions in ΣSGAR residues in barn owls in 2022 suggests that full implementation of stewardship since 2018 has yet to result in a statistically significant reduction in exposure of barn owls to SGARs

Concentration and origin of lead (Pb) in liver and bone of Eurasian buzzards (Buteo buteo) in the United Kingdom.

Ingestion of lead (Pb) derived from ammunition used in the hunting of game animals is recognised to be a significant potential source of Pb exposure of wild birds, including birds of prey. However, there are only limited data for birds of prey in Europe regarding tissue concentrations and origins of Pb. Eurasian buzzards (Buteo buteo) found dead in the United Kingdom during an 11-year period were collected and the concentrations of Pb in the liver and femur were measured. Concentrations in the liver consistent with acute exposure to Pb were found in 2.7% of birds and concentration in the femur consistent with exposure to lethal levels were found in 4.0% of individuals. Pb concentration in the femur showed no evidence of consistent variation among or within years, but was greater for old than for young birds. The Pb concentration in the liver showed no effect of the birds' age, but varied markedly among years and showed a consistent tendency to increase substantially within years throughout the UK hunting season for gamebirds. The resemblance of the stable isotope composition of Pb from buzzard livers to that of Pb from the types of shotgun ammunition most widely-used in the UK increased markedly with increasing Pb concentration in the liver. Stable isotope results were consistent with 57% of the mass of Pb in livers of all of the buzzards sampled being derived from shotgun pellets, with this proportion being 89% for the birds with concentrations indicating acute exposure to Pb. Hence, most of the Pb acquired by Eurasian buzzards which have liver concentrations likely to be associated with lethal and sublethal effects is probably obtained when they prey upon or scavenge gamebirds and mammals shot using Pb shotgun pellets

Long-term trends of second generation anticoagulant rodenticides (SGARs) show widespread contamination of a bird-eating predator, the Eurasian sparrowhawk (Accipiter nisus) in Britain

Second generation anticoagulant rodenticides (SGARs) are widely used to control rodents around the world. However, contamination by SGARs is detectable in many non-target species, particularly carnivorous mammals or birds-of-prey that hunt or scavenge on poisoned rodents. The SGAR trophic transfer pathway via rodents and their predators/scavengers appears widespread, but little is known of other pathways of SGAR contamination in non-target wildlife. This is despite the detection of SGARs in predators that do not eat rodents, such as specialist bird-eating hawks. We used a Bayesian modelling framework to examine the extent and spatio-temporal trends of SGAR contamination in the livers of 259 Eurasian Sparrowhawks, a specialist bird-eating raptor, in regions of Britain during 1995–2015. SGARs, predominantly difenacoum, were detected in 81% of birds, with highest concentrations in males and adults. SGAR concentrations in birds were lowest in Scotland and higher or increasing in other regions of Britain, which had a greater arable or urban land cover where SGARs may be widely deployed for rodent control. However, there was no overall trend for Britain, and 97% of SGAR residues in Eurasian Sparrowhawks were below 100 ng/g (wet weight), which is a potential threshold for lethal effects. The results have potential implications for the population decline of Eurasian Sparrowhawks in Britain. Fundamentally, the results indicate an extensive and persistent contamination of the avian trophic transfer pathway on a national scale, where bird-eating raptors and, by extension, their prey appear to be widely exposed to SGARs. Consequently, these findings have implications for wildlife contamination worldwide, wherever these common rodenticides are deployed, as widespread exposure of non-target species can apparently occur via multiple trophic transfer pathways involving birds as well as rodents