Birds Might Have a Built-In Head-Up Display Overlaying Navigation Data Onto Their Vision

"It’s long been known that birds have a sense for the Earth’s magnetic field and can use it to aid in navigating their long migratory routes across the continents, but researchers at Oxford University and the National University of Singapore think their innate navigation tools are even cooler than once supposed. A new study shows that birds may actually see that magnetic field. In other words, birds have a natural head-up display akin to that used in fighter jets and other aircraft that overlays information on their fields of vision."