A 'hobby'
Twenty five years a professional
You see, you've made a serious error there, Barn Owls are in fact one of the most seriously effected species, along with kestrels.
The bait kept down permanently for rats is actually being eaten by small mammals, like woodmice and fieldmice, which are in turn being predated by Barn Owls and Kestrels.
For many years now, residues of rodenticides have been found in liver samples taken from dead birds. There is very little actual evidence that these residues are causing deaths, but the BoP lobby have made as much of it as they can.