Owls kill 10 to 20 percent of mouse populations every year

Evidence

Diligent biologists can harvest these pellets and pick through them, counting and identifying bones, to reconstruct an owl’s diet on any given night. A single owl can eat four or five mice a night, and well over a thousand in a year. Scaled up to the landscape, owls kill between 10 and 20 percent of mouse populations in a typical year—up to one-fifth of all mice die in the talons of an owl. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 29