Near miss

I live in a house with cats, but probably wouldn't choose to if I was living alone. My other half likes them, so I share my living space with three at the moment.
It creates a dilemma. If I feed the birds in my garden, am I exposing them to an unnecessary degree of risk? Predation by a sparrowhawk is one thing, but being killed by a bored cat is quite another.
On balance though I think the benefit that comes from a reliable source of food through the winter outweighs occasional losses to one of our moggies. And our collection of cats are on the whole elderly and too slow for bird-catching.
My partner's latest cat acquisition arrived as a kitten last winter. An unwanted pet, it decided we were a better bet than its first owner.
He's now got his own bed, name (Boris) and territory. He's also at that time of life when hunting is a full-time occupation.
This morning we were enjoying a cup of tea in bed when there was a squawk from downstairs. As I went down, Boris was coming up - with a mouthful of downy feathers.
At the bottom of the stairs more feathers and bird droppings. I searched the area for a dead bird, but then heard clucking in the kitchen.
Our dog was looking at a male blackbird that was sitting on top of our microwave.The bird had lost a couple of tail feathers, but otherwise looked relatively unscathed.
When I opened the kitchen door the blackbird flew out, relieved to have made it back into the garden alive. I later saw it feeding, but don't rate its chances of long-term survival.
What toll do wild populations of birds and mammals suffer at the paws and claws of bored domestic cats? Not sure if anyone can say with any degree of accuracy, but on the whole cats and wildlife gardens really don't mix.