The only proven humane approach to controlling feral (outdoor, free-roaming, barn) cats is trap/neuter/return (TNR).
Cats are trapped, sterilized, vaccinated and returned to their environment.
LCHS, Inc. has traps to loan to assist you in TNR.
Calling Animal Control about feral cats, or trapping and taking these cats to shelters, often leads to their being euthanized. It also creates what is known as a “vaccuum effect,” meaning it just makes space for other feral (unvaccinated, breeding) cats to move in.