What are you talking about Pikey?
It's clearly a habitat issue in the first instance which is probably why the wildlife of France is still better than that of the UK, simply because there is more space and a greater diversity to start with. Threats and losses here are the same though, we are losing habitat, mainly to hedgerow loss, monoculture, loss of wetlands, (50% in the last 50 years), loss of ponds, (used to be several for each small group of houses, 90% gone in he last 50 years).
Cats are an introduced non native species, just as are mink, american crayfish, grey squirrels, harlequin ladybirds and so on. Invariably introduced species have a detrimental, if not catastrophic affect on native species, hence the increase in cats is not natural. Perhaps it would be better to shoot cats rather than Corvids?
Chris