birdie on the moon. Not literally, of course. Theres no actual birds up there. But thats not what Charles Morton thought.
In 1703 he published a pamphlet claiming that the reason some birds disappeared during winter
was because they were vacationing on the moon.
Really puts the loon in lunar [MUSIC] Throughout history, people were at a loss
as to why some birds appeared out of nowhere in the spring only to disappear again during
winter, and when it came to explaining why, their common sense flew south. Aristotle figured that certain birds didnt
leave at all, they just changed from one type to another. And a medieval scholar said geese
began life as barnacles, while another claimed they blossomed from trees every spring. The poet Homer accepted the fact that cranes
embarked on great journeys, but instead of seeking warmer weather it was to battle tribes
of mythical goat-riding dwarves at the ends of the Earth.
I am NOT making this up. Fittingly, the answer to this avian enigma
was delivered by a stork. Storks were, and still are, a common sight in Europe during
summer, except most dont have spears hanging out of their necks. After this unlucky bird
was shot in Germany, for a second time mind you, the origin of the spear was traced to
sub-Saharan Africa, proving once and for all that birds spent their winters in warmer climates.
And not the moon.
Birds dont use calendars, as far as we
know, so how do they know when to take off? By tallying observations about their environment
like changes in daylight, average temperatures, and the amount of food that there is to eat,
a biological switch is triggered that tells the bird its time to pack its feathery
bags. These days, scientists use technology ranging
from leg bands to GPS to map their incredible journeys. The arctic tern takes the longest trip of
any bird, covering as much as 50,000 miles in a single year between its Arctic and Antarctic
nesting grounds. Bar-headed geese have to cross over the Himalayas
on their annual journey, the highest migration of any bird.
To survive at those extreme altitudes,
theyve evolved specialized hemoglobin, and like other birds, they have a special
one-way respiratory system that keeps fresh air running through their lungs all the time. The great snipe is a migration speedster,
covering more than 4,000 miles at speeds up to 60 mph, while the bar-tailed godwit completes
its 7,000 mile, eight-day journey across the Pacific without stopping once, powering its
trek by packing on more than half its body mass in fat. One of the worlds most amazing bird migrations
is undertaken by one of the smallest: the ruby-throated hummingbird. Before these petite
pilots embark across the Gulf of Mexico, they too add more than half their penny-sized body
weight in fat too, and during their 600 mile trip, they burn off a quarter of their body
mass in just 20 hours! Its hard to keep weight on when you have to flap your wings
50 times a second.
Flying V! The flying V might be hockeys greatest
formation, but its also a trick to fly more efficiently. When a bird flaps its wings,
it creates a rotating vortex off the wingtip. If the bird behind is in the right place,
it can get a free boost from that updraft. Whats crazy is that birds can somehow sense
where that vortex is, and they actively flap their wings to stay in the sweet spot.
Birds are able to navigate the globe with
amazing accuracy, some returning to the same nesting spot year after year. Pigeons taken
far from home, sealed in isolation chambers cut off from light, outside air and magnetic
fields, were still able to find their way back. Its easy to see how birds might draw
a map, but what about a compass? Some birds have been found to use the sun, and others
the stars. But for many birds, they are the compass.
Tiny iron-rich crystals were discovered in
the eyes and beaks of many birds, and scientists now suspect that these allow birds to sense,
or maybe even see Earths magnetic field. We may have had some bird-brained ideas about
where our where birds disappear to, but thanks to science we know the truth is as good as
any myth. Maybe better. Stay curious..
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