The semi-communal nesting and loquacious nature would suggest to me that they're Harris Hawks; the white tail tips and undersides pretty much confirm it.

You shouldn't have them in Minnesota, but if there's a raptor center releasing birds to the wild, it seems possible.

http://www.desertmuseum.org/visit/rff_harris.html

or, completely tangentially,

http://danny.oz.au/travel/scotland/duncansby-dunrobin.html

-- Graydon, who does after all owe you a few wild-thing identifications