ABSTRACT
In the early 1920s, blue tits across Britain were observed stealing milk from the bottles on people’s doorsteps by prizing up, or pecking open, their foil tops (Fisher and Hinde 1949). While this behavior alone is interesting enough, its spread through blue tit populations is striking, because birds all over the country adopted the behavior so rapidly that only some form of social transmission could explain it. Indeed, subsequent research into blue tit milk-bottle-opening has shown that the transmission of the trait between individual birds, along with its maintenance in populations over multiple generations, was 1 dependent on a form of social learning – specifically, local enhancement (Sherry and Galef 1990; Sherry and Galef 1984). 2
