"Alas, all our little friends up this way in MN seem to have left already." Trust me, they're all here. In fact, I have some that aren't (from the books) suppose to be here, western birds, probably lost.
Aha, this might be a fun learning experience then. See if they fight more than you normally see. I'm not for sure, but I'm guessing the different types of hummers might act differenty.
Sorry to say I don't don't diddly about bluebirds.