Where I live do that you trap them they spay them and they can return to their home ..they will collect them I am told ,all you do is place the trap out and let them know when they come to collect they the cats are feral and only need fixing they will test for sickness..
Check your area for shelters, animal welfare groups, even vets that do TNR. You can rent traps, take them in to be spayed/neutered, then take them back and release them, usually at no cost to you.
No, there is no general birth-control for cats, only spaying/ neutering and euthanasia.