Years ago my father finally became fed up with the huge number of strays around his house and bought a Havahart trap. He rapidly lost track of how many he trapped & turned over to animal control, but at the beginning, it was not uncommon to go out during the day and count 20 to 30 strays/ferals visible at one time. One or more of the neighbors was putting out food for them.The animal shelter folks finally came out to reduce the numbers, via trapping. In a period of just over a month, from the nearby woods, they trapped seventy-two (72) cats. Seventy-two!
It was interesting to see the local small wildlife populations slowly recover when the cat infestation was eliminated.
What's really insidious is that the normal predator/prey balances do not exist for feral cats when people feed them. In a normal situation, a predator population rise results in a prey population drop which, in turn, causes the predator population to drop as well. The system has a built-in feedback control system that insures the predator can not wipe out the prey population. When people feed feral cats, that control system is lost. The predator population is not dependent on the prey population for sustenance. That allows predators to hunt their prey into extinction