SUPPOSEDLY, this occurred in the 1950s some time.
There was a terrible football rivalry between MIT and Harvard on the football field. One Summer, an MIT student noticed that the MIT/Harvard game was the first on the roster in the Harvard ballfield in the coming school year. So, for several weeks before the game, the MIT student dressed up in black-and-white strips like a referee, snuck onto the Harvard football field and blew a whistlke, and then threw bird seed onto the grass.
Before long, thousands of birds, and then tens of thousands of birds, were perched on the fence every day at the Harvard football field, waiting for the "ref" to appear, and blow his whistle.
On opening day in the Fall, the stands were filled with thousands of people, mostly from Harvard, of course. The teams came onto the field, and the referee dressed in black-and-white stripes blew his whistle.
Suddenly, tens of thousands of birds descended on the field around the ref, tweeting and squawking, dropping happy little bird poops everywhere!