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Bird migration has puzzled people for centuries. While Indigenous communities developed rich lore around the movement of birds, knowing exactly where birds went and why was mostly guesswork in ancient times—though some came closer than others. As early as the fourth century BCE, Aristotle aptly that “birds migrate from the steppes of Scythia to the marshlands south of Egypt,” referring to the migration of Common Cranes from Iran. But in the absence of concrete evidence, about birds hibernating at the bottom of lakes and journeying as far as the moon persisted—until the pfeilstorch.

In the spring of 1822, a White Stork caused a stir among the townspeople of Mecklenburg, Germany. The species commonly ranges throughout Europe during the summer, but when this particular bird landed on the property of a local landowner, something about it stuck out: specifically, a 30-inch spear—tip and all—poking vertically straight through its neck. The bird, which had somehow survived the injury, lingered for a few days before being shot down by a hunter. 

According to , a German science magazine, the stork's body ended up in the zoological collection of the University of Rostock, where botanist Heinrich Gustav Flörke performed an examination. Describing the spear as one with “a broad iron tip attached with sinews” and “very fine-veined tropical wood,” Flörke concluded that the bird was likely impaled while wintering in the “Upper Nile Region”—modern day Sudan—where such spears were commonly used in hunting and warfare. Now known as the pfeilstorch (German for “arrow stork”), the taxidermied bird remains on display at the University of Rostock. Though the most famous example, it apparently wasn’t the only White Stork spotted sporting arrow fragments, with perhaps upward of  such birds observed.

While the Rostock pfeilstorch is considered the first tangible proof of long-distance migration by birds, it didn’t change our understanding of the phenomenon overnight, says bird expert and author Scott Weidensaul. “There wasn’t necessarily an ‘aha’ moment, but lots of incremental discoveries,” he says. Direct knowledge of migration increased with European exploration of the global south, where many birds spend their winters. And some travelers, such as English naturalist Henry Baker Tristram, learned from locals with existing avian awareness. On a in the Sahara, Tristram  “the natives are perfectly familiar with the fact of the swallow’s migration, as they say go visit Timbuctoo.”

In addition to field observation, the pfeilstorch served as a strong clue for researchers that birds spend time in other, faraway places, but it wasn't until scientists began banding birds that many of the lingering mysteries around migration began to be solved. Using uniquely coded aluminum rings popularized in Europe, scientists were better able to keep track of individual birds and understand how many of them returned each year. ​​The United States Geological Survey's Bird Banding Laboratory expanded bird banding across the United States, helping to establish the ideas of migratory flyways. By the end of the 19th century, recordings of nocturnal flight calls proved that birds primarily migrate at night and produce different calls to help their flock stay together.

More recently, satellite and radio tracking technology have given us an even more of where birds go and how they travel. “It’s one thing to say that birds generally spend their winters in warmer ����APPs, but to know where specific bird species go is an entirely different thing,” Weidensaul says. For example, we now know where White Storks  and can track their exact routes back and forth.

The pfeilstorch was an early and very obvious example of the travel clues birds can carry with them, but with advancements in science, we have found other, more subtle hints. In a 1979 study, researchers identified in the songs of European Marsh Warblers the songs of  they likely came across while wintering in southeast Africa. Techniques like stable isotope analysis advanced our knowledge further by decoding the chemical signatures birds pick up on their journeys. Nowadays, we can even track how their gut microbiomes change along the way. 

While the pfeilstorch often garners only a footnote in most ornithology histories, its impact on bird migration research is undeniable. “The pfeilstorch carried this rather gruesome evidence of where it spent its winter.” Weidensaul says. “It will always be such an iconic—if not, dramatic—story.”