Your, "Guardbird", is a Northern Mockingbird. They are NOTORIOUS for driving away ANYTHING they think could oose a threat to them and their, "Territoty". My resident Mockingbird, Mr. Mocky, who has lived in my yard for the last five years has faithfully been driving away EVERY Starling that has DARED come into or near our yard. He is fairly tolerant of other birds. He just HATES Starlings. I noticed your Mockingbird is on top of the suet cage. SUET is the thing a Mockingbird will defend MOST Vigorously!
Mockingbirds are known for attacking many birds, dogs, cats, and even lawnmowers! I had one that would swoop down and land, one foot from me, every time I mowed the yard, a few years ago. But if you put out apple slices on a platform feeder from time to time, you can change your Mockingbird from a potential enemy, to a loyal friend. A couple of weeks ago Mr. Mocky brought by a little surprise for me.
Meet......MR. MOCKY, JR!!!
Mr. Mocky, Jr.