Picus was a son of Saturn and the father of Faunus. The sorceress Circe fell in love with him but he did not respond to her approaches. As a result she lured him to a forest and turned him into a woodpecker, Latin picus.
In some stories he appears as a sooth-sayer who made use of a woodpecker in his predictions. The bird was in fact regarded as having powers of prophecy, no doubt for its ability to 'tap out' the future. It may be no coincidence that Circe's name means 'hawk'.