While humans erect more and more physical boundaries around the world, birds just carry on cheerfully ignoring them. The brother and sister team Dries and Bieke Depoorter took thousands of photographs of these winged border-crossers by first training artificial intelligence to recognize them in video footage. With this AI, they monitored publicly accessible surveillance cameras at several politically sensitive borders: between Mexico and the United States, Morocco and Spain, Greece and Turkey, and France and England.