As for predation on birds by cats. Sure it happens a lot. It is not something in isolation of other impacts. There is also a lot of predation on birds by birds
(butcherbirds, raptors etc) and other animals. Predation is a thing that happens anyway. To some extent it will reduce mortality pressures from other factors. Most species do plenty of breeding to sustain themself through predation. Sure cats add to it and
for some prey species, that are particularly vulnerable, it is a significant concern, especially when made more easy due to habitat loss and fragmentation.
Philip
