Well cats are definitely highly in-homogeneous hunters and some do A LOT and others very little. I'm sure the high end of that number is counting strays but I've known cats to grab a bird a few times a week. The thing is that many cats aren't showing you their spoils. Also, remember that cats sleep most of the day and their hunting is primarily done at limited hours. Though (indoor/)outdoor cats tend to be more active. You're probably not going to meet these cats though unless you've been to a rural area. Barn cats tend to be pretty effective predators. If you're in a bigger city, well there's not going to be as many birds (less opportunities) and you're probably less likely to see the spoils as if you have an adverse reaction one time then they won't show you again. They're just bringing back home a toy, not a meal.