Those are wild chickens.  My husband and I see them often.  Here's a link to an article about them from the Post-Gazette: http://www.post-gazette.com/pg/08247/908917-53.stm.  I'm not sure who (if anyone) is feeding them now that the school has closed.
-------------- Original message from Megan Branning <meganbranning@yahoo.com>: --------------

I spotted one or two chickens near the little park on Black Street today. I wonder if these are the same chickens someone lost recently? Thought I better say something just in case.