Our 4 year old spayed female cat has starting bringing live and dead birds home. It seems to make no difference whether she has a bell collar on or not. She had never brought anything in until the last couple of weeks and since then it's been a dead bird on the back doorstep (we have a 'lean to'),one dead bird in the living room and two alive birds in the living room. Is this just normal behaviour? I've heard this is something to do with maturity and mothering but I'm not sure. Can I do anything to stop it?