Bluejays are beautiful. I love them. They're aggressive birds and will dive at cats and dogs whom they see as threats. I had a Sheltie dog who used to run around a tree in my back yard and the bluejays made a habit of diving at her as she barked! I've seen the same done to my "Yellow Kitty."
My neighbors have numerous bird feeders in their back yard, and the variety of birds there is amazing and beautiful to watch. I haven't installed bird feeders because of my cat, who would love to catch them. The same neighbors had a bird feeder in their front yard dogwood tree, and my cat would stand on the bannister and leap to catch the birds. (They removed that bird feeder!) In their back yard, the birds are safe, because their Rhodesian Ridgeback dog guards them!