Scientists have made an unusual discovery inside fossilised dinosaur droppings: a bird feather. It comes from a period 66 million years in the past. It is thought to have been left by a Tyrannosaur. The feather is exceptionally well preserved, which is a rare find. The find offers direct proof of the predator's meal. The feather shows the dinosaur had eaten a bird. This might help explain how some birds survived the mass extinction. These findings are detailed in a new scientific study. It gives us a snapshot of ancient predator-prey interaction.