It's too bad that TNR couldn't be used in your country (you must have a hell of a feral population); as I understand it, once you get to a 90 percent neutered-spayed level in any discrete feral group, especially if female spays are the majority, it begins to collapse; there simply aren't enough fertile females having kittens, and the high level of feral kitten deaths means that even the non-spayed or neutered females won't replicate fast enough to offset the permanent decline.

That may not work in a place where there aren't discrete feral groupings, and it does require some up-front capital costs.