The Blue Tit Effect was a phenomenon discovered around the 1950s. Bird watchers and milk lovers alike noticed that Bluetits were pecking through milk bottle caps on doorsteps to get to the delicious cream inside. The Blue Tit turned out to be the only bird that did this consistently. The amazing part? It turned out that this was a learned behaviour, passed from Blue Tit to Blue Tit. Robins gave it a go, and some succeeded, but failed to pass it on to any other robins. This means (well we like to think it does) that originally there was just one brave, pesky blue tit who took the plunge. Others watched, and went off to try it themselves. This is known as the Blue Tit Effect.