I don't have a cat . . .

One of the biggest problems I can see with most of the studies is that they only focus on one aspect of the ecosystem (feral cats or wildlife). You see the change in the cat population but don't measure the change in the wildlife population (you assume a result on wildlife based upon changes in the cat population). Wildlife studies focus on the wildlife without really monitoring the changes in the cat population. Population predictions usually assume no migration into the colony; an unrealistic assumption in most regions. Both groups (animal welfare and wildlife conservation) need to work together to find the best solution for the entire ecosystem, not just their interest (feral cats vs. wildlife). That, being said, doing nothing is not a viable solution.

At this point I have strayed long enough off topic and will stop here.