For hundreds of years, farmers around the world have built scarecrows to guard their fields, and the idea is surprisingly simple: dress a stuffed figure to look roughly human, prop it up among the crops, and hope that passing birds mistake it for a real person and stay away. Most scarecrows are built from a wooden cross frame stuffed with straw, old clothes, and sometimes a stuffed sack for a head, but farmers have always looked for ways to make them more convincing. Some tie strips of shiny foil or old cassette tape to the arms, since the flashing movement and glinting light in the wind startles birds more than a still figure ever could. Records suggest some farms have built scarecrows towering more than 10 metres high, far taller than any real person, simply to be visible from every corner of a large field. The trouble is that birds are clever, and most learn within a week or two that a motionless figure is never going to chase them, so many farmers move their scarecrows to a new spot every few days to keep the birds guessing. In recent years, some farms have swapped straw figures for gas-powered noise cannons or drones shaped like hawks, but the traditional straw scarecrow, however old-fashioned, is still a familiar sight across the countryside every harvest season.