A small anecdote from our farm seems to match the theory about the damage from mesopredators.
Our closest neighbor had many (20+?) feral barn cats. I would frequently see them on our property and I think our quail/pheasant numbers were far below what they should have been considering our habitat.
We started seeing bobcat signs on the property about 2-1/2 years ago and have had numerous sightings since then. The barn cat population seems to have suffered a significant decline over the same period. In fact, I have not even seen a cat in the neighbor's yard this year.
Our bird population has significantly increased over this same time period. However, there are many other variables - we came out of a drought, etc.
I don't know if the bobcats ate the feral cats to eliminate hunting competition, or if they just found them to be easy prey. Either way, it appears that a family of bobcats eats fewer birds than multiple families of feral house cats.