The Blue Jay is a very colorful blue; they can be down right mean at times.
Here is a few links to help Identify and understand there behavior.

http://www.birds.cornell.edu/BOW/BLUJAY/

http://www.passporttotexas.com/birds/oct.html

http://www.nhptv.org/natureworks/bluejay.htm

http://www.realindy.com/bluejays.htm

http://www.wbu.com/chipperwoods/photos/jay.htm

http://www.nenature.com/BlueJay.htm

Brokenwing.