The cover of Wolfgang Haug’s 1986 book Critique of Commodity Aesthetics bears a striking photo — when corn was strategically spread in in St. Mark’s Square in Venice, hundreds of feasting pigeons produced an impromptu advertisement for Coca-Cola.

Evidently Coke had borrowed the idea from Assicurazioni Generali, a Venetian insurance company with headquarters in the piazza. The insurers would coax the pigeons to form the letters A G.

I’m not sure when the Coke ad was made. In The Postmodern Arts: An Introductory Reader (1995), Nigel Wheale says the ad could be seen on the walls of Italian bars and restaurants in the late 1960s, but possibly the photo had been taken earlier.