IMO cats should be kept in at night especially during spring when they target fledgelings at sunrise which are an easy target as they are not 'streetwise'. That would be a good start. You can buy a cat flap that you can set so that once a cat comes in after a certain set time, say 8pm in the evening, and it can't get out again until whatever time you decide in the morning. Cats soon get used to it, mine did.
Also, a collar that snaps free when caught on anything, with as big a bell as you can find to give the birds some warning time, should be worn.
Bird feeders in gardens are of course a target for birds and therefore cats, so the feeders should be placed carefully, high up and near a tree or a bush so a bird can seek protection in the foliage.
Anything that might save the lives of our lovely song birds is worth a try. Lots are on the RSPB's Red list as endangered. Cats are not on anyone's endangered list.