A while back the British carried out a study of how house cats affect the small bird and other animal populations, and they were astounded by the vast numbers of these other animals the cats wiped out. Cats are highly efficient killers.
But this being said, the solution to this is not to kill cats or restrict them to the indoors. Instead it should be to breed *replacement* birds, especially, to repopulate and even overpopulate for the losses.
Captive breeding for release is very successful in restoring wild populations of both plants and animals. Done right, so many are released that even with a high attrition rate, eventually natural controls come into play.
It also has the double side effect of increasing the populations of predators that prey on them; but by doing this, to reduce the numbers of unwanted animals, such as mice and rats.
This area used to have tons of Whip-poor-wills, but they are all gone. Haven’t heard one in years and years. They nest on the forest floor, so I think replacement whip-poor-wills released into the wild would just be more prey for the cats if the cats population isn’t decreased. I think the feral cats and owned cats that are allowed to roam killed them all off.
Freegards