Other predators- this list doesn't have all the predators, but has some of the most common culprits.
Hawks Hawks kill birds and small mammals. The only thing you can do if you have hawk problems is have your feeders close to cover, like pine trees, so the birds can hide when a hawk comes by.
Owls Owls usually come out at dusk, preferring mice and other small mammals that are out at night. They are a very good rodent control system. The best thing to do to make sure it doesn't come after your birds is to have cover close to your feeders.
Cats Cats kill so many birds, I have put them on their own page. Click here to go to their page.
Anything that eats bird eggs/young The best defense against these pests is to have a tall, slick metal pole with a wide baffle on which to mount your bird houses.The pole should be at least seven feet tall, and it should not be made of wood.