The version of the story that I heard was that some British company was building a high speed train and wanted to test it against bird strikes. They borrowed a chicken cannon from an American aerospace company (the cannon being a standard item for testing aircraft canopies) and were horrified to see how much damage the train was taking. The Brits sent the footage to the Americans for review and the Americans simply responded: "Gentlemen, thaw your chickens."
They tested this pretty thoroughly on Mythbusters. The final result being that frozen chickens get much better penetration then thawed ones.