Lesson 1 The Wonders of Nature
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Winged Wonders: Amazing Facts about Migratory Birds
Geese flying south in a V shape is perhaps the classic picture of bird migration.
But this image only represents a fraction of the real picture.
The reality is that humans know less about bird migration than they think they do.
How Much Do We Really Know about Migratory Birds?
Many believe that, like humans, birds migrate during the day.
But most birds migrate at night.
Every year, billions of birds fly through the darkness over us while we are asleep.
If we stripped away the darkness, we could see what would probably be the largest natural spectacle on the Earth.
Roughly half of the world’s nearly 10,000 known bird species migrate.
You might think migratory birds fly long distances only, but many migrants make shorter journeys.
Some even migrate from a higher part to a lower part of the same mountain.
Migratory birds contribute much to our ecosystem.
For example, they pollinate crops and help plants grow by scattering seeds and eating insects.
Some resident birds do these things as well.
In addition, certain areas, such as the Arctic, heavily rely on migratory birds to maintain their ecosystems.
While scientists have made meaningful progress in the study of migratory birds, questions about their incredible abilities remain largely unanswered.
Despite our familiarity with bird migration, it remains one of the great puzzles of the natural world.
How Do Birds Prepare for Migration?
As migratory birds prepare for a long journey, some undergo incredible physical changes.
Bar-tailed godwits, for example, eat all the time and double their weight before their 12,000-kilometer journey from Alaska to New Zealand.
They look like water balloons because they have accumulated so much fat under their skin.
At this point their digestive organs shrink dramatically, but their heart, lungs, and leg muscles double in mass.
They bulk up without even exercising!
The godwits then fly all the way across the Pacific Ocean without a break.
They have no place to land during this journey, so they must constantly flap their wings for more than a week.
After landing in New Zealand or Australia, they regrow their digestive organs, feed again, and regain their weight.
They then fly up to the Yellow Sea located between Korea and China.
There, they go through the same process of bulking up before flying back to Alaska.
How Do Birds Navigate?
Migratory birds can cover thousands of kilometers on their seasonal travels, often traveling the same course with little deviation.
The secrets of their amazing navigational skills are not fully understood.
This is because birds are believed to combine different types of senses when they navigate.
Researchers think that birds get navigational information from the sun’s position, the patterns of the stars, and landmarks seen during the day.
Sensing the Earth’s magnetic field is believed to be another navigational tool.
Researchers suspect that a specific protein in the birds’ eyes is sensitive to magnetism.
All of these, however, are hypotheses that have yet to be proven.
How Do Birds Fly without Stopping?
In 2013, researchers presented the first evidence that migratory birds like Alpine swifts can fly without a break for over six months.
They captured six Alpine swifts, put monitoring devices on them, let them go, and recaptured three of them after a year.
To the researchers’ surprise, the data gathered by the equipment indicated that the birds had most likely flown without landing for 200 days.
Alpine swifts feed on aerial plankton so they need not land for food.
But what about sleep?
The data implied that the birds had slept during flight but that this was not full recovery sleep.
They may have been in a state where half of their brain slept while the other half remained alert.
Some birds have this special ability, and it enables them to sleep and navigate at the same time!
What Hazards Do Migrating Birds Encounter?
Migratory birds are facing a growing threat from humans.
Many species migrate at night and are attracted to the lights of tall buildings.
As a result, millions die after colliding with such structures.
Many are also killed by wind farms.
Especially problematic is the destruction of mudflats by humans.
Mudflats are important stop-off locations that provide food supplies critical to birds’ survival.
The largest tidal mudflats on the Earth are the Yellow Sea mudflats in Korea and China.
However, these mudflats are fast disappearing as humans turn them into land.
This has become one of the world’s greatest conservation concerns for migratory birds.
We have done much harm to migratory birds.
But despite everything we have thrown at them, these birds have taken it all and are still obeying the ancient rhythms and doing the things that they were always meant to do.
Such wonders of nature deserve respect.
We need to show that by doing what we can to protect birds.
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