I believe I can help with this, since when I was a student I was the "Chicken."

Mostly it came about because the Institute (under SAJ's tutelage) tried to change the name of all sports teams, with the exception of hockey, to the "Red Hawks." She wanted to change the hockey team name too, but alumni threw a hissy and threatend their all important donation dollars, so a compromise was reached. This change was brought about because they didn't want to be known as just an engineering school. There are actually Red Hawk nests on the roof of the Pittsburgh building and others, so the name makes sense. The Red Hawk appeared at football and baseball games, and oter campus events, and tried to appear once at a hockey game, but it didn't go over so well and he never appeared there again. At one point, the Red Hawk was even being considered for "Meanest Man On Campus" during GM Week. At football games, chants of "KFC" and "Frank Perdue" arose from the stands, and the band even started playing The Chicken Dance, to which the very handsome and smart guy in the costume played along. Eventually, the Institute realized what a mistake it was making and changed all teams back to "Engineers," and the Red Hawk, or Chicken, was to never be seen again.