This woodland bird normally eats insects.  However, during the year 1929, the British blue tit developed a remarkable new appetite -- for stolen milk!

Residents of the British town of Swaythling were the first to notice birds prying the wax-board seals off freshly-delivered milk bottles on their doorsteps and drinking the cream that floated to the top.  The behavior was tracked over the next 20 years as it gradually spread throughout the entire United Kingdom.

Flocks of blue tits began stalking neighborhood milk trucks, and their digestion underwent evolutionary adaptation to this new, richer food source.  Yet, the behavior died out abruptly within a few short years when the U.K. finally adopted new containers that the birds' beaks could not penetrate.

Statistical analysis of the spread of the phenomenon suggests the birds did indeed learn the tactic by watching others, although the behavior probably did not start with a single bird.

The episode is often used as an example of a "meme" -- a novel idea that spontaneously appears and is transmitted throughout a population.  Robins also learned the trick of opening milk bottles, but the "meme" never became widespread among this species -- perhaps because the equally-resourceful robins lacked the social skills of the tits, whose flocking habits may have made them more adept at observing one another.