Rodenticide levels in Common Kestrels (Falco tinnunculus) and Barn Owls (Tyto alba) in north-west Spain

Beatriz Rubio Alonso

Master's thesis

Abstract:

Anticoagulant rodenticides (ARs) have been commonly used for rodent pest control in the past decades. This extended use has an impact on non-target species that are exposed to these products through primary or secondary poisoning, especially predatory bird and mammal species. Biological control of rodents through the increase of natural predator populations is an ecological and economic solution to the damage rodent pests cause in agriculture and the negative ecological consequences of the use of ARs. We have studied the presence and levels of ARs detected in two species of birds of prey: common kestrel (Falco tinnunculus) and barn owl (Tyto alba); sampled from installed nest boxes in Castilla y León, located north-west of Spain, for the biological control of common vole (Microtus arvalis). The blood samples were analysed using a one-step QuEChERS-based extraction method using acidified acetonitrile, followed by two complementary analyses: a liquid chromatography analysis coupled to triple quadrupole mass spectrometry (LC-MS/MS) and an analysis by gas chromatography coupled to triple quadrupole mass spectrometry (GC–MS/MS). Out of the 11 different types of ARs analysed, 7 of them had positive results, meaning these compounds are persisting in the environment and penetrating the food chains. All these compounds have been forbidden for agricultural use, although the domestic and industrial use of most of them is currently still legal. The most detected ARs were brodifacoum and bromadiolone. The levels between the two species did not differ statistically, and neither did the correlation between the levels of AR and the results of the haematology. However, further studies with a bigger sample size would be necessary to make conclusions on these aspects. The concentrations differed statistically between the specific compounds. Highly elevated concentrations were found for coumachlor and coumatetralyl. Biomonitoring studies are important to monitor the use of pesticides and to evaluate the effects on the local fauna. These findings give us an overview of the impact of ARs in birds of prey in the study area and help working towards solutions against the present human-wildlife conflict.

Keywords

rodenticides, birds of prey, human-wildlife conflict, secondary poisoning

Language used: English

Date on which the thesis was submitted / produced: 22. 4. 2022

Thesis defence

• Supervisor: doc. Ing. Karolína Brandlová, Ph.D.

Czech University of Life Sciences Prague

Faculty of Tropical AgriSciences

Master programme / specializace:
Wildlife and Livestock Production, Management and Conservation / Wildlife Management and Conservation