Battle of Cats and Birds

2 years ago we adopted a small feral cat colony and have spayed or neutered each kitten and the 2 mother cats (when we finally trapped them). We feed the entire colony of about 20 plus any visiting neighbor cats, but this still doesn't prevent these cats from killing the birds that live on our 5 acres. I wish there were some way to stop this, but most of our finches, quail and other birds have moved somewhere else.
We have been able to tame one young feral cat who was over one year when he was first introduced inside our house and now lives indoors every night with the rest of our 4 indoor cats. He is very affectionate and has an "indoor" personality and an "outdoor" spookier personality. He was never destructive inside and used a litter box from the beginning. There are also 3 other ferals that will allow me to pet them when they are in the right frame of mind. I believe that taming ferals just depends on their personality. We have always fed them kibbles but every evening I put out some small pans of canned food for them and they really look forward to this, even start gathering an hour or more before the usual time. These cats are very easy going and never fight with any strange cats that happen by.

There have been many, many studies that show that habitat loss, pollution and other "human" actions do more harm to the birds than cats do. Also, I disagree that feral cats cannot be tamed, it may take some time and patience, but there have been cases where they have become so attached to their caregivers that they do become pets. In most feral colonies, the cats are well fed and do not want to hunt, they would rather laze around and watch the birds instead of killing them. All of my cats are totally inside, which is the best way of all, but some people just don't "get it". There are many ways to keep an inside only cat happy and stimulated. Inside cats have longer, healthier lives.