Barn owls eat mice, rats and various other small mammals, helping to keep the rodent population under control as nature intended. During outbreaks of the rat / mice population, Barn owls will breed...
They Eat Rats That Are Delicious nom nom nom
Yup, plus shrews, rabbits, voles, ect.
because they taste nice :P
A pair of Barn owls... can have up to 9 babies... a family of 11 owls have been known to kill and eat up to 20,000 mice in a year.