【Native Speaker每日综合训练—43系列】【43-09】科技 Migration

cherry6891

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Part I: Speaker

Birds May See Earth's Magnetic Field
Birds have sensory mechanisms that apparently allow them to see magnetic fields, which may explain the apparent ease with which they migrate thousands of miles to specific locations. Cynthia Graber reports.
October 1, 2007
Millions of birds each year heed the call of changing seasons and migrate thousands of miles from one feeding ground to another. Scientists have shown that the earth’s magnetic field helps guide them. But how? Research now suggests that birds may literally see this magnetic fly plan. Scientists at a university in Germany previously demonstrated that a particular molecule that senses magnetism exists in birds’ eyes. A later study showed that these molecules and a frontal part of the brain are active in the presence of a magnetic field. Now, their latest study links the two. They published their results in the journal Public Library of Science ONE.

The researchers traced the path of the neurons from the eyes into a specific part of the brain.  Both the path and the brain region are active during magnetic orientation. The tracers attached to the neurons showed that these areas are linked by a well-known brain circuit involved in vision. The scientists caution this isn’t definitive proof. But it is a pretty strong suggestion that birds can somehow see their way along the magnetic fields that surround the globe. That’s quite a bird’s eye view.

source:
http://www.scientificamerican.com/podcast/episode/5a6f5359-e7f2-99df-3ef566b01a023131/
[Rephrase 1 1'20'']

cherry6891

Part II: Speed

time2
Flight Insurance: What Is Being Done to Protect Migratory Birds?
Chief among environmental threats to migratory birds is habitat destruction
July 3, 2011
Dear EarthTalk: What are the major issues with protecting migratory birds that groups like the Nature Conservancy are working on?—Lorinda Bennet, Albuquerque, N.M.

Migratory birds, like other animals, need suitable habitat and food sources to survive. But unlike other animals which stay primarily in one place, migratory birds depend on the availability of food and habitat all along their migration paths, which for some are thousands of miles long. Changing environmental conditions along routes can hinder birds’ ability to survive their often arduous long distance journeys.

Some 1,800 of the world’s 10,000 bird species migrate long distances every year. Typically birds fly to the far north in the summer to feed and return south for the winter to breed, but many variations and exceptions exist. The long-distance record holders are Sooty Shearwaters, which migrate 9,000 miles between nesting sites in the Falkland Islands and feeding sites in the North Atlantic Ocean off of Norway.

Chief among environmental threats to migratory birds is habitat destruction. Human development of wetlands areas leaves many birds without suitable habitat for stopovers and even wintering sites. Global warming only twists the knife by making usual stopover sites even less hospitable. Biologists see that widespread climate change is already starting to have a negative effect on the timing of migration cycles and breeding patterns, leading to population declines in species already considered threatened. Hunting is another threat to birds which pass over countries without the resources or will to enforce protections. Obstructions such as power lines, wind farms and offshore oil rigs also negatively affect migratory birds. [262 words]
time3
A large number of international treaties and domestic laws provide protection for migratory birds. For example, the Migratory Bird Treaty Act of 1918 affirms the U.S. government’s commitment to international conventions protecting migratory birds (and their eggs and nests) passing through Canada, Japan, Mexico and Russia at some point during their annual travels. Upwards of 1,000 different bird species, as listed on the U.S. Fish & Wildlife Service’s Migratory Bird Program website, are protected under this Act. A similar treaty called the African-Eurasian Migratory Waterbird Agreement seeks to protect migratory birds along another of the world’s major migratory bird flyways.

While governments only do so much to protect migratory birds, private non-profits are working hard—and devoting millions of dollars—to try to take up the slack. One of the leaders in this battle is the Nature Conservancy, which employs hundreds of ornithologists and planners who identify networks of habitats needed by bird species throughout North America, Latin America and the Caribbean and then work to protect these crucial areas for current and future generations of migratory birds.

Conservancy projects focus on important ecosystems, from the grasslands of the Great Plains to the pine oak forests of Central America and points beyond, identifying and protecting a network of high-quality stopover habitats around the Gulf of Mexico as well as along the Pacific Coast of the U.S. and Canada—and studying how climate change and other environmental factors affect bird migration throughout the Western hemisphere.[244 words]
source:
http://www.scientificamerican.com/article/protecting-migratory-bird/

Reanalysis of 4-Winged Dinosaur May Illuminate Evolution of Bird Flight
By Kate Wong | October 23, 2012
time4
RALEIGH, N.C.—How did the ancestors of birds evolve the ability to fly? That birds are descended from small, meat-eating dinosaurs is established. Exactly how the creatures conquered the air remains a mystery, however. Now the authors of a new study of a controversial feathered dinosaur say they have resolved a key aspect of the problem—namely, how the animals controlled their flight once they became airborne.

Two theories have dominated the long-running debate over how bird flight evolved. In the so-called cursorial scenario, the ability to fly emerged in terrestrial dinosaurs that raced across the ground with their arms outstretched and leaped into the air after prey or out of harm’s way, their wing feathers providing lift. The arboreal scenario, in contrast, supposes that flight arose in tree-dwelling dinosaurs that were built for gliding and started flapping their arms in order to stay aloft longer.

In 2003 a feathered dinosaur fossil came to light that was purported to elucidate the question of how flight evolved. The roughly 125-million-year-old specimen exhibited evidence of feathers on its hind limbs in addition to its forelimbs, prompting researchers to describe the crow-size animal, Microraptor gui, as a four-winged dinosaur. A startling artist’s reconstruction accompanied the description of the fossil remains, showing the bird flying with its hindlimbs spread out to the side, as if doing a split. The authors argued that the feathered hindlimbs, together with the forelimb wings, acted as an airfoil to help the animal glide. Critics begged to differ.

The new work paints a different picture of how Microraptor’s enigmatic hindlimbs functioned. In two presentations given on October 20 at the annual meeting of the Society of Vertebrate Paleontology (SVP) in Raleigh, N.C., Michael Habib and Justin Hall of the University of Southern California argued that the hindlimbs would have been generally held under the body during steady flight and then deployed to produce rotation movement (roll) or left-right movement (yaw) during unsteady maneuvers such as turning. The team reported that its mathematical modeling indicates that Microraptor’s hindwings would have enabled it to turn twice as fast as a two-winged animal—handy for dodging trees in its cluttered environment. Complimenting the hindlimb’s role in turning and braking, the tail of Microraptor controlled up-down movement (pitch), the researchers say. “A combination of pitch control by the tail, roll generation by the ‘hindwings’ and multi-purpose control by the main wings would have made Microraptor a highly maneuverable animal,” Habib noted.
[409 words]

time5
“This study provides a plausible mechanism by which dinosaurs that otherwise have strongly Velociraptor-like bodies could take to the air and control themselves while in flight,” Hall remarked in a statement to the press. “Obviously crashing is bad for the long-term health of the animal, but until now we had little idea how the earliest flying dinosaurs avoided such catastrophes given their relatively simple wing structure.” Habib added that this so-called distributed control system may have been an independent experiment in flight that had no bearing on the evolution of bird flight, or that it could represent an intermediate phase in the evolution of bird flight, after which most control function shifted to the forelimbs. The presentations were co-authored by David Hone of the Queen Mary, University of London, and Luis Chiappe of the Natural History Museum of Los Angeles County.

Not everyone is convinced by the team’s arguments. Kevin Padian of the University of California at Berkeley, an expert on bird evolution, observed that the presentations focused on the effect of the hindlimb on a gliding animal instead of one that flapped its wings. Last year at the SVP meeting he presented evidence that gliders and flyers are completely unrelated to each other. He says that “there is not a shred of evidence that says gliding is involved in the evolution of flapping flight.” He questioned why the team’s model would focus on gliding parameters when the forelimb shape was consistent with flapping, not gliding, and the hindlimb would have generated so much drag.[255 words]

source:
http://blogs.scientificamerican.com/observations/2012/10/23/reanalysis-of-four-winged-dinosaur-may-illuminate-evolution-of-bird-flight/

As Fishes Migrate, Their Food Might Not Follow
Ocean species seeking cooler waters to survive may have to adapt to their new environments by changing their diets
September 25, 2012 |By Mark Fischetti
time6
Monterey, Calif.—As Earth's atmosphere heats up due to global warming, the world's oceans will warm, too. All kinds of creatures, from the smallest plankton to the largest fishes, will be forced to adjust. Some of them may be able to adapt by altering their body chemistries, but the most likely response—for those that are free to travel (unlike oysters, say)—is simply to move.

Indeed, certain species of fish are migrating away from mid-latitude oceans toward cooler waters such as the Arctic Ocean, according to recent studies. Scientists are finding that, in general, larger ocean organisms such as fishes have less tolerance for temperature change than the microorganisms they consume, such as phytoplankton. So it is possible that as fishes migrate, their preferred food sources may not. To survive, the migrants may have to change their diet once they reach their new neighborhoods. Some of the most recent findings are being released for the first time at a symposium here this week called The Ocean in a High-CO2 World.

Of course, the fishes that already live in colder oceans may not appreciate the arrival of newcomers that could compete for their food. Yet the native species have their own challenges. Research is showing that fishes native to colder waters are even less tolerant of temperature changes than those in warmer waters, according to Hans-Otto Pörtner at the Alfred Wegener Institute for Polar and Marine Research in Germany. "The temperature range that fish are comfortable in decreases as latitude rises," he says. Over time, then, the mix of species could change. In cold northern waters, for example, sardine populations are dropping but anchovy populations are rising.

Other factors come into play: Increasing carbon dioxide emissions worldwide are making all oceans more acidic, forcing species to use more energy to adapt, leaving them with less energy to reproduce and grow. Oxygen levels in certain ocean regions are dropping, adding a third stressor to acidification and temperature rise. Scientists are beginning to unravel how these multiple stressors are affecting species across large spans of ocean, but much more data and analysis is needed. In the meantime, increasing numbers of species may be on the move. What they will eat once they reach their destinations, and which ocean inhabitants they may have to compete with, remains to be seen.[387 words]
source:
http://www.scientificamerican.com/article/as-fishes-migrate-their/

cherry6891

Part III: Obstacle

Technology Unlocks the Mysteries of Bird Flight
By Starre Vartan | September 24, 2014 |  
Bob Dylan asked: “Are birds free from the chains of the skyway?” Sure, this is a metaphor (in Dylan’s case, for a lost love) but it works because the complexities of avian flight—from migration and navigation to group dynamics—have long been a mystery, one with a preponderance of ideas, but few firm answers. Of course, insects and mammals also developed flight, in one of the great examples of convergent evolution, but bird flight in particular has long fascinated and mystified.

Homer and Aristotle both recorded details of bird migration; but human interest in bird flight probably goes back much further in time, if you go by indigenous people’s myths and legends. As long as there have been people watching birds, there have been theories as to how and why they do what they do. In the modern era, theories about why birds flock and why they migrate in v-formations have abounded, yet answers have been few. But new research using creative technology on both starling murmurations and bald ibis’ migration reveals that complex flight dynamics and rapid-fire adjustments based on sensory feedback previously believed impossible for birds are indeed occurring.

Built-in GPS? Not so fast
Bald ibises made the cover of the January 16, 2014 issue of Nature when researchers answered one of the biggest questions about how and why the birds migrate in a v-formation.

“For 50 or 60 years, there have been plenty of entirely theoretical papers which predict where birds put themselves in the v-formation,” says Dr. Steven Portugal, a postdoc in avian flight at University of London’s Royal Veterinary College (RVC). But nitty-gritty details were difficult to capture, and the data was incomplete: “Previously,people had used photos and videos, which doesn’t give the right accuracy. Those can distort height, if they were flying in the same plane, and it misses information. It only gives you snapshot of a flight as opposed to a dynamic image.”

Portugal’s team worked with the Structure and Motion Lab at the RVC on a built-from-scratch flight logger, which synced a 300-hertz accelerometer with a 5-hertz GPS and was light enough to attach to a bald ibis (it had to be less than 5 percent of the bird’s weight to ensure it wouldn’t unduly impact behavior). The combination of these two systems enabled the researchers to see exactly where the birds were and what their wings were doing by taking measurements at high frequency.

The team attached the loggers to 14 young ibises that were being reintroduced by a conservation group, the Waldrappteam, to their former range in Austria and Germany. The birds had to be taught their migration route and flew at intervals behind an ultralight plane. While most songbirds instinctively know migration routes, larger birds like pelicans, cranes, geese and ibises need to be taught where to go by their parents—or in this case, the conservationists. It was a unique opportunity to be able to track how the birds flew (and logistically far simpler than catching wild bald ibises).

The results from the loggers, taken over a 45-minute flight, revealed something previously believed, but never definitively proven: The birds timed their wing flaps and positioned themselves relative to other birds to maximize efficiency. “The main finding was not only that they position themselves in the best possible position for catching updraft, but that it’s an active process. The wingtip of a bird following another takes the same path as the one in front, so they adapt when and how they flap to capture as much upwash as they can,” says Portugal.

Engineering for the birds
Dr. George Young is a mechanical engineer who has closely examined starling murmurations (those giant flocks of coruscating birds that viral videos are made of) to understand optimal group behaviors—and not just to answer questions about how and why the small birds flock as they do (interesting enough), but because that information could be useful to his work in designing non-biological intelligence. “We’re looking at how we can design groups of sensors or robots to allow them to do something sophisticated and intelligent for cheap,” says Young.

Starlings could provide the answers Young needs, since they have solved the problem of communicating over large groups with plenty of (information) noise. Young calls this kind of work, “bio-inspired engineering” – using nature’s solutions to solve ongoing quandaries.

While it was known that in starling flocks each bird pays attention to its seven closest neighbors, what wasn’t understood was why. In a January 2013 research paper in PLOS Computational Biology Young and Naomi Leonard, his PhD advisor at Princeton (where he was pursing his doctorate), as well as colleagues from Sapienza University in Rome, determined seven is the number that “optimizes the balance between group cohesiveness and individual effort,” according to the paper.

“Essentially, if the bird is paying attention to too few neighbors you can’t pass information through the whole flock. If a bird is watching too many, they’re not getting more information, they’re just paying the cost. Six or seven is the minimum number of neighbors you need in a group to keep the flock connected,” says Young.

To figure out the magic number, Young used video data that was analyzed frame-by-frame. The position and velocities for each bird in the group were tracked and plotted. “We took that position data and used that to reconstruct hypothetical interaction networks,” says Young. And then some creative use of technology came into play.

MatLab, a program widely used in engineering for stress analysis and fluid dynamics, was familiar to Young as an engineer, but in his starling research he used it to simulate biological systems instead. “We ended up working on a very large matrix, with a row and column for each bird, but MapLab has its own programming language that allows you to quickly code up large computations” like those coming from hundreds of starlings in a murmuration, says Young.

By using an engineering program for biological analysis, the magic number was found, and Young hopes to apply this knowledge to other systems that are dealing with signals and noise, as starlings do so effectively. “The fact that the same number of neighbors is optimal over a range of flock sizes and densities—as well as, to a certain extent, typical flock thicknesses—suggests that the number of neighbors that a bird interacts with could be an evolved trait,” says Young.

Speaking of evolution, what could be a more perfect example of where we are now than an engineer using software to understand a natural solution to a problem that will eventually make smarter robots?[911 words]
source:
http://blogs.scientificamerican.com/guest-blog/2014/09/24/technology-unlocks-the-mysteries-of-bird-flight/

AgendaChen

Time2+3
The author discusses the threats that migratory birds have to face in recent years and the way in which people try to save those birds.
At first, the author introduces the migratory birds: a kind of special species which has to migrate thousands of miles to survive and breed. Then, the author tells us three threats to these birds: human development, global warning, and hunting. In the end, the author gives some efforts of how people try to protect the migratory birds, including law protection from government and additional efforts from non-government. The author focuses on the projects of Nature Conservancy, a private non-profits that works very hard to protect these birds.
2m47s

Time4+5
The passage introduces a possible way in which small dinosaurs fly. Proponents use Microraptor gui as evidence. In the beginning, the author mentions the other two theories: cursorial scenario and arboreal scenario. And then, the author begins to introduce the Microraptor. It is a four-winged dinosaur because its forelimbs and hindlinbs have feathers, thus both acting as an airfoil to help the dinosaur glide. Respectively, the hindlimbs help the animal roll and move left-right, the forelimbs are the main wings for multi-purpose, and the tail controls up-down movement. In the past, the scientists don't know how dinosaurs control the flight. But now, thanks to the fossil, the scientists find a plausible explanation.
However, Kevin Padian opposes to this explanation, and instead he believes that this fossil only unveils the mystery of how dinosaurs gilde but not how these creatures flight.
5m

Time6
As the global temperature goes up, the fishes that can't resist higher temperature have to migrate to cooler region of the ocean. However, their food, microorganisms, has higher tolerance for temperature change than them does. Therefore, once the fishes move to a new habitat, they have to adapt new diets. The author also introduce the three stressors the fishes may fave: competition for food with native fishes, increasing acidicity in the ocean because of increasing carbor dioxide emissions, and decline of oxygen level in the ocean.
1m55s

Ob
The mysteries of bird's flight has perplexed scientists for many years. Now, by using advanced technology, scientists are able to unlock the mysteries.
The author gives us two example. The first one is that  scientists use GPS to analyze the behaviour of bald ibises and eventually figure out how and why the birds migrate in a v-formation. The second one is that Dr. Young use Matlab, a software for engineering analysis, to understand why each starling pays attention to its nearest seven neighbors when flying.
8m3s

awillleadaway

生词很多，新人表示看得头晕眼花，结构神马的暂时分不清楚，第一步暂时只能把每段能记住的用简单词汇记下来。
P1
Scienctists study the principle of bird immigration from one feeding place to another, a German science team has learned that birds recognize the destination through a neural path from eyes to brain to feel the magnetic fields.

P2
3’31
Talk about some respectives factors that have negative effects for the migration of birds. Nearly half bird species have the habit of migrating, and enormous variations and environmental changing during their path result obstacles. Besides these factors, global warming and human activities have resulted even more negative effects, deverioting the conditions of stops that are critical for surviving immigration jouney.  What is more, hunting during the path is also a important element to decreasing the numbers. In this case, some species are threatened extictions.
3’32
A number of international treaties and acts were issued to protect the migration of birds. For example, a act in 1918 arose to protect the flyway through U.S., Canada, and Mexico. And another example for international act to protect waterbirds’ stopover habitats through the migration path.
5’32
Discuss how the birds concory征服 the sky, the established theories is that birds are evolved///decended进化from small dinosores恐龙

How this kind of dinasors恐龙 learned flying. Two contrast theories had debated for years. One considered it is a terrestrial species//breed，and the other construed it as a tree-dwelling one who could gliding with its wing and learned to flap in order to stay longer in the air.

A new discovered fossil revealed the secret. It has four wings and two other organs that enable it to do something fly-evolving actions.

Some professors from North California University explained another possibility when these wings and organs functioned.
3’57
A expert presented that this theory above may seem plausible nowadays, but only one problem that this body structure is bad for flapping for long-term was unable to sovlve, so the fly model of the earliest dinosaurs was unkown. He was support by a professor in London University.

However, another expert in bird evolution in a university disagree, claiming that the body structure of gliding has no bearing on that of flapping, this hindlimb and forelimb structure was obviously could not be possible for flapping. And there is no related revolution process connected these two.
5’35
As the ocean temparetures turned higher and higher due to the global warming, some fishes or marine animals may have the ability to change their body chemistries to adopt this environmental change, but most of them the only adoption is moving.

The scientists have learned that smaller organism has less tolerant for the water temperature while the bigger has not, thereby proving the diet that migrating fishes might have to change when they reach a new neighborhood. And what is more, the native fishes of the cooler water may not appreciate of the new comer who will compete food with them. Some data have already shown that after this kind of competition some species may be more prosperous, some may decrease dramatically.

The study of this issue is still underway, and more data are needed to reveal the answer to questions on this topic.

P3  13’27
Some focus on birds’ fly principle that remain secret and their v-fomation. First, it introduces some former methods that is not very efficient, then the second passage mentioned a university team 发明a equipment that is no heavier than 3 pencent of a bird’s wing weight, they anlonize分析 the data received from the equipment set on home-raised ibiris. The reason to choose this specy种类 is because young ibiris need to learn the migration path form its parent. And the data prove some previously believed thought,V-formation is most efficient shape when flying.

Some engineer tried to study the efficiency of bird fly to apply it to robot or new machines. After studying the recording frame-to-frame, He found birds are generally connected with 7 neighbors which is the minimum number needed to be consistent with information surpassed during the whole flock. Then the end seem to need more to be seen.

seraph797979

cherry6891 发表于 2014-10-21 07:59
Part II: Speedtime2
Flight Insurance: What Is Being Done to Protect Migrator ...

2.1‘37
3,1’31
4,3‘03
5,1’30
6,2‘29

cherry6891

43-09
Time2
chief among environmental threats to migrate birds is habitat destruction.
Time3
International treaty and domestic laws provide protection to the migrate birds.
Conservancy projects focus on the ecosystem
Time4
How the animal controlled the flight once they have airborne?
time5
Two Theories dominated how bird flight evolve. One is cursorial scenario,the other is arboreal scenario.
Then the feather fossil elucidate how flight evolved. Later,new work paints how the hind limbs functioned.
That is a plausible mechanism of birds flying but it can not explain how the bird avoid crashing in air. And not everyone is convinced by the argument
Time6
The food won't go together with migrant fish,so migrants need to new environment

Obstacle
Technology unlock the mysteries of bird flight.
Why and how the birds migrates in a v-formation? The bird timed the wing flaps and  positioned .

The information why small flocks are together can be applied to biological intelligence.

Olivia的monde

T2 2/18/49
T3 1'52'32
T4 3/37/72
T5 1'34'88
T6 2/55/17
Obstacle: 6/06/39
1.the metaphor of Bob Dylan- bird flight in particular has long fascinated and mystified.there have been theories as to how and why they do what they do.(past-modern)-now,new research using creative technology on both starling murmurations and bald ibis’ migration
2.Bald ibises: how and why the birds migrate in a v-formation.
Dr. Steven Portugal and his team  built-from-scratch flight logger-see exactly where the birds were and what their wings were doing by taking measurements at high frequency. track how the birds flew,
result:prove:The birds timed their wing flaps and positioned themselves relative to other birds to maximize efficiency.
3.Dr. George Young:solved the problem of communicating over large groups with plenty of (information) noise. bio-inspired engineering,
4.Paper in plos: seven is the number that “optimizes the balance between group cohesiveness and individual effort,” according to the paper( Young used video data that was analyzed frame-by-frame.)
5.MatLab,familiar to Young, but used  it to simulate biological systems instead.(own programming language to code up large computations)
6.call for  a more perfect example understand a natural solution to a problem-smarter robots
速度变慢了。。。。。。。

efilwen

time 2: 2''29'''
Some birds fly to south in winter and back to north in summer to search for food. However, human activities are posting great threat to the migration of birds. The development of wet lands destructs the habitat of some birds and leaves them no suitable places for stopover sites, leading to the reduction of birds population. Besides, the changing climate and hunting by humans are also causing the decline of the number of birds.

time 3: 1''30'''
Governments, organizations and individuals are making effort to protect migratory birds. International treaties have been made to protect major migratory birds flyways and stopover habitats in different countries. Non-profit NGOs are organizing professionals to protect the ecology environment around the habitats of migratory birds.

time 4 : 3''08'''
It has long been known that birds are descended from dinosaurs, but it was still a mystery that how they evolved wings and the ability to fly. A recent study that illustrates the structure of ancient birds and functions of their limbs might illuminate this mystery and offer some hints for further study.

time 5: 1''47'''
The results of the recent study sound plausible and explain some long-time questions. However, the study is challenged by some other experts of bird evolution, who question the focus and reasoning of the new study.

time 6: 2''38'''
Global warming is changing the diet habit of fishes in the oceans as fishes that used to live in warmer areas are moving to colder regions to adjust themselves to the changing environment. However, their new habitats do not provide them with regular foods and they also face the competition from existing species in the new home, making them to alter their diet habit. Besides, the global warming also makes the sea water more acidic and less oxygen-rich. All of these factors have changed and will continually change the ecology of the ocean and oceanic creatures.

obstacle: 10''
Scientists have been studying how migratory birds adjust their velocity, height and V-shape with other birds and have found that birds doing those through sensory feedback. Loggers have been used to track the routine of migratory as well as the time of wing flapping and relative positions in the flying queue. Scientists finally find the magic number, an optimal number that one could communicate with others.  

油桃F

Speaker
Birds have molecules existing in their brain so that they could see magnetic field when migrating.

[Time 2] 2'03
[Time 3] 1'21
Migratory birds are deeply influenced by food and habitat, which may be threatened by human development. Several countries published some laws to protect these birds. Protection is focused on ecosystem.

[Time 4] 3'48
[Time 5] 2'11
A study showed birds evolved from small dinosaurs. There are two theories. First one indicates gliding and the other proposes a control system. Not everyone supports the idea. One person said gliding is unrelated to flapping.

[Time 6] 2'36
Animals choose to move when facing changeable temperature. Large animals and species that live in cooled areas are less likely to adapt to changeable environment. Global warming results in more CO2 and leaves less O2 for animals to reproduce.

Obstacle
Birds' migration is mysterious.
Scientists used new methods which were more accurate than that in the past to learn v-formation.
Scientists found a magic number-seven-which means migratory birds connect with their seven neighbors through technological programs.