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In May of 1822,
Count Christian Ludwig von Bothmer
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shot down a stork over his castle
grounds in North Germany.
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However, he wasn’t the first person
to hunt that specific bird.
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Upon recovering the stork,
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von Bothmer found it impaled
by a yard long wooden spear.
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A local professor determined
the weapon was African in origin,
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suggesting that somehow,
this stork was speared in Africa
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and then flew over 2,500 kilometers
to the count’s castle.
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This astonishing flight wasn’t just
evidence of the stork’s resilience.
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It was an essential clue in a mystery
that plagued scientists for centuries:
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the seasonal disappearance of birds.
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Ancient naturalists had various theories
to explain the annual vanishing act
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we now know as migration.
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Aristotle himself proposed
three particularly popular ideas.
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One theory was that birds transformed into
different bodies that suited the season.
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For example, summer time garden warblers
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were believed to transform
into black caps every winter.
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In reality these are two distinct species—
similar in shape and size,
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but never appearing at the same time.
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Over the following centuries, birds
were said to morph into humans,
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plants, and even the timbers of ships.
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This last transmutation was especially
popular with many Christian clergy.
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If barnacle geese were truly made of wood,
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they could be deemed vegetarian
and enjoyed during meatless fasts.
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Aristotle’s second and even more enduring
hypothesis was that birds hibernate.
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This isn’t so far-fetched.
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Some species do enter short,
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deep sleeps which lower their heart rates
and metabolisms.
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And there’s at least one truly
hibernating bird:
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the common poorwill sleeps out winters
in the deserts of North America.
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But researchers were proposing much more
outlandish forms of hibernation
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well into the 19th century.
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Barn swallows were said to remove
their feathers and hibernate in holes,
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or sleep through the winter at the bottom
of lakes and rivers.
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Aristotle’s final theory
was much more reasonable,
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and resembled something
like realistic migration.
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However, this idea was also taken
to extremes.
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In 1666, the leading migration advocate
was convinced that each winter,
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birds flew to the moon.
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It might seem strange that prominent
researchers considered such bizarre ideas.
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But to be fair, the true story
of migration
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may be even harder
to believe than their wildest theories.
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Roughly 20% of all bird species
migrate each year,
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following warm weather and fresh food
around the planet.
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For birds who spend their summers
in the northern hemisphere,
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this journey can span
from 700 to over 17,000 kilometers,
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with some flights lasting as long
as four months.
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Birds who migrate across oceans may soar
without stopping for over 100 hours.
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Sleeping and eating on the fly,
they navigate the endless ocean
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by the stars, wind currents,
and Earth’s magnetic field.
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Tracking the specifics of these epic
expeditions is notoriously difficult.
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And while birds often take
the most direct route possible,
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storms and human development
can alter their paths,
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further complicating our attempts
to chart migration.
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Fortunately, Count von Bothmer’s stork
offered physical proof
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not only that European storks were
migrating south for the winter,
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but also where they were migrating to.
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Ornithologists across the continent
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were eager to map the trajectory
of this flight,
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including Johannes Thienemann.
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Owner of the world’s first permanent
bird observatory,
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Thienemann was a major public advocate
for the study of birds.
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And to solve the field’s biggest mystery,
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he wrangled an army of volunteers
from across Germany.
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His team used aluminum rings to tag
the legs of two thousand storks
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with unique numbers and the address
of his offices.
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Then he advertised the initiative
as widely as possible.
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His hope was that word of the experiment
would find its way to Africa,
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so people finding the tags would know
to mail them back with more information.
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Sure enough, from 1908 to 1913,
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Thienemann received 178 rings,
48 of which had been found in Africa.
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Using this data, he plotted the first
migration route ever discovered,
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and definitively established that storks
were not, in fact, flying to the moon.