Or a human who is tired of his small children picking up literal cat feces from the feral cat who is pooping in their planters. I would recommend looking up Toxoplasma Gondii.

You can also enjoy this classic comic to help re-align you on how many birds cats kill: https://theoatmeal.com/comics/cats_actually_kill

Isn't the purpose of planter boxes to grow living things?

Plants are living things.