Question for Birders

[montanacowboy]

I just put out a new Hummingbird Feeder on a Shephard's Hook. I also have another feeder which serves as a bottom Hummingbird Feeder and the top is a regular Seed feeder for birds.
Ever since I put the new Hummer feeder up I seemed to have attracted a little tyrant. There is one Ruby Throated who sits atop the Sherphard's Hook and will not allow any other Hummers to come near it. He sits there literally all day long in pouring down rain and wind and attacks any other birds that attempt to feed.

Is this normal HBird behavior? Also does anyone know why the ruby triangle on its throat turns black?