Songbirds are restless creatures, and scientists have learned to take advantage of that trait to study their migration. In one famous experiment, researchers place a bird in a cage equipped with sensors. When night falls, the bird jumps in the direction in which it would normally migrate, allowing researchers to determine where it would like to go. But in 2004, in a German lab at the University of Oldenburg, the classic experiment failed miserably. The European robins that the researchers were using simply wouldn't orient themselves in a single direction. "We tried to change the food the birds were getting, the light, the cages — just about anything," recalls biologist Henrik Mouritsen. "Nothing had any effect." For the next three years, Mouritsen and his team tried to figure out why the robins weren't orienting.