It's just natural for them. Our two year old female is a good hunter but this month she seems to have declared all out war on the local wildlife population. So far we have had:-
12 voles.
2 shrews.
2 field mice.
7 birds.
Yesterday she was busiest with 2 voles, a bird and a field mouse. The thing is that most of these are alive and brought into the house. The rodents are easy to catch as she usually have them cornered and it's just a matter of picking them up and letting them go back into the field. The birds though are a completely different matter. She comes through the kitchen door into the hallway and drops them on the front door mat. You can imagine the chaos that follows. Poor terrified little bird flying around the house with me and a manic cat trying to catch it.