So how do you guys know these are feral cats? Because they don't have a collar?
The old lady across the street had 20+ outdoor cats before she died 5-6yrs ago. All the rabbits had disappeared from the neighborhood while the cat reigned and I 'm sure the owl that lived on one of my trees didn't help with the rabbit population either. Now all those cats are gone as well as the rabbits but some neighbors still have 1-2 cats each. I see at least 3-4 different cats walk through my property every day but they are not causing any problems. Sure they stop and look around, hide in my bushes, etc. but eventually after 1/2 hour or so they leave. 2 of them tried sleeping by my trees & bushes in the back & front but I didn't let them. I chased them away until they learned this is not a hotel. They get the picture after a while and they have very good memory.
There is still a healthy squirrel population in the neighborhood here so it doesn't seem like these house cats are able to catch them or hurt their #'s. I guess feral cats have to live off the land and would kill more critters for food than a house cat would, so I can see them causing a lot more problems. The squirrels around here play with the cats. They let them get pretty close before running up a tree, and even then the squirrel hangs out only 8-9ft up and laughs at the cat. I have seen a cat climb up a tree, sneak up on a squirrel and catch him when I was teenager but that cat was like 1 in a million. She was a supreme hunter, only weighed like 2-3lbs and was lightning fast. She would bring home all kinds of animals. One time she was eating a large sea bird in our backyard that was at least 1.5X her size.
Anyway I think trapping the ferals with a cage is probably the best course of action but I 'm sure you 'll get 1 or 2 house cats in there. If you see posters on the telephone poles 1-2 days later, you know you caught someone's pet :-)