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3 bizarre (and delightful) ancient theories about bird migration

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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.
Title:
3 bizarre (and delightful) ancient theories about bird migration
Speaker:
Lucy Cooke
Description:

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Video Language:
English
Team:
TED
Project:
TED-Ed
Duration:
05:20

English subtitles

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