Pfeilstorch
A Pfeilstorch (German for "arrow stork") is a stork which is injured by an arrow while wintering in Africa, and then returns to Europe with the arrow stuck in its body. This Pfeilstorch was crucial in understanding the migration of European birds. Before migration was understood, people had no other explanation for the sudden annual disappearance of birds like the White Stork and Barn Swallow. To date, around 25 Pfeilstörche have been documented.