Outdoor cats eat outdoor birds. You could look it up. But if they live indoors as your pets, the birds start acting like they can do anything they like to any cat, and get away with it. None of my cats ever had the opportunity to live with birds. I hope it didn’t stunt their growth.
My son has stray cats who come to the back yard and he feeds them there, but the birds
join in and take their share. Neither birds or cats seem to mind the party looking odd.
I’ve seen many a bird caught by cats, though–how do they know it’s safe to come down?