Scarecrows are villains from the series Doctor Who. They were man-like figures intended to deter crows from eating crops. These ones are villains that are a army of soldiers created by a group of family called the Family of Blood.
They are animated scarecrows as mindless soldiers through the power of molecular fringe animation in rural 1913 England.
Jeremy Baines of Farringham School for Boys had already stumbled across their ship and had his body taken over by Son of Mine.
The Family then used scarecrows to abduct humans to be used as bodies for the incorporeal Father, Mother and Daughter.
The scarecrows were used as an army to attack Farringham School for Boys, where many were shot down. Eventually, they re-animated to do morthe Family's bidding. They were presumably made inanimate again after the Family's defeat. Son of Mine was himself turned into an immobile living scarecrow (of a different kind) by the Tenth Doctor.