For the first time, Chinese and foreign research teams have accurately revealed the migration pattern of Beijing swifts
. From leaving Beijing in mid-July every year to returning to Beijing in late April of the following year, the round trip is nearly 30,000 kilometers, covering 37 countries.
Recently, a tracking study on the migration behavior of Beijing swifts was officially published in the international journal "Movement Ecology", which for the first time accurately revealed the migration ecology of Beijing swifts.
Every April, Beijing swifts arrive in Beijing from southern Africa to build nests and breed, and then return to southern Africa for wintering from the end of July to the beginning of August.
Which countries did the nearly 30,000-kilometer migration route pass through?
How do researchers obtain this data?
In this regard, a reporter from the Beijing News interviewed Professor Liu Yang, the corresponding author of the paper and an ornithologist from the School of Ecology of Sun Yat-Sen University.
Wear a miniature photosensitive locator for Beijing Swift
Beijing swift, the common swift Beijing subspecies (Apus apus pekinensis), is a wild migratory bird named after "Beijing".
Studies have shown that every April, Beijing swifts arrive in Beijing from southern Africa to nest and breed, leave Beijing from the end of July to the beginning of August, and return to southern Africa for wintering.
However, which countries did this migration route with a round trip of nearly 30,000 kilometers pass through?
Are there stopping points?
What's the weather like along the way?
Little was known for a long time.
According to Liu Yang, the research project was carried out by researchers from Beijing Normal University, Sun Yat-sen University, Lund University in Sweden, the British "Swift Action" team and the Royal Belgian Academy of Natural Sciences, as well as the China Biodiversity Conservation and Green Development Fund. It is jointly implemented by volunteers of the Bird Watching Professional Committee.
From 2014 to 2018, the research team successively wore miniature photosensitive locators for 66 Beijing swifts at Kuoruting in the Summer Palace in Beijing.
With the help of this low-consumption recycling device that records light intensity and performs positioning and tracking according to the law of day and night changes, the researchers successfully recovered and analyzed the light intensity data of 25 individuals.
The migratory round-trip flight covers 37 countries in Asia and Africa
The data shows that most of the autumn migration of Beijing swifts begins in mid-July. They leave Beijing, enter Mongolia in the northwest, and then enter the northern part of Xinjiang in the west, enter Central Asia from the Junggar Basin, cross the Red Sea in mid-August, and arrive in early September. Central Africa, a short 40-day movement within the Congo Basin or adjacent areas.
Then it slowly went south, and finally reached the wintering place in early November, the South African plateau at an altitude of about 1,000 meters. The whole journey was 14,733 kilometers and took 111 days.
After ending the 100-day wandering life during the wintering period, Beijing Swift began to move northward rapidly in mid-February of the following year and stayed in the eastern Congo Basin for nearly a month.
Then, they turned to the northeast, left Africa in early April, traveled day and night, and returned to Beijing in late April, covering a total distance of 13,572 kilometers and 64 days.
During the entire round-trip migration process, Beijing Swift's flight covered 37 countries in Asia and Africa.
Beijing Swifts stop for 2-6 times during the autumn migration
People used to think that Beijing Swifts would go straight to their destination during their migration without stopping.
However, the findings suggest that this is not the case.
It is known that the average daily moving distance of common swifts is usually more than 250 kilometers.
If the moving distance within 3 days is less than 500 kilometers as a stop, then the autumn migration of Beijing Swifts will stop 2-6 times in the middle of the migration for 71 days, with an average migration speed of 134 kilometers per day; the spring migration will stop 1-2 times and stop 36 times in the middle. days, with an average migration speed of 217 km/day.
The Congo Basin and its surrounding areas, the southwestern coast of the Red Sea and the southern coast of the Caspian Sea are the three most important resting areas.
Judging from the flight trajectory, Beijing Swift may have taken a more direct migration route and a faster flight speed in spring.
■ Dialogue
Ornithologist Liu Yang:
At two o'clock in the morning, the swift locator was recovered at the Summer Palace
"If you want to protect a bird, you must first understand its behavior." Therefore, the members of the research team wanted to find out where Beijing Swifts went after they left Beijing.
But collecting their migration data is not an easy task, from choosing a suitable tracking locator to capturing swift recycling data.
Liu Yang told reporters that every time they capture, they have to go to the net at 2:00 in the morning, and not every locator released can be recovered. It took 4 years and finally recovered the data of 25 Beijing Swifts.
The miniature photosensitive locator is only 0.67 grams and is easy to wear
Beijing News: How does the miniature photosensitive locator work?
What are the advantages?
Liu Yang: At different places on the earth, the times of sunrise and sunset are different.
When the sun rises, the light gradually becomes stronger, and when the sun sets, the light gradually becomes weaker.
According to the data recorded by the miniature photosensitive locator, through some calculations and analysis, we can deduce the approximate position of Beijing Swift.
The advantage of the miniature photosensitive positioner is its lightness.
Because birds cannot wear locators that exceed 3% of their body weight.
Beijing Swifts generally weigh 30-40 grams, less than an egg.
The miniature photosensitive locator is only 0.67 grams, which is convenient for Beijing Swift to carry on its back.
However, the photosensitive locator also has shortcomings. Compared with satellite navigation, it is not accurate enough and has errors.
In addition, we also mentioned in the paper that around the vernal and autumnal equinoxes of the lunar calendar, day and night are almost the same length.
Therefore, the measurement of the photosensitive locator in these two days and the days before and after it is not very accurate, but the impact on the overall long-distance travel of Beijing Swift is not particularly large.
Beijing News: Is the data sent back in real time or does it need to be recycled for reading?
Liu Yang: The photosensitive locator itself does not emit a signal, and the device needs to be recovered to download data, which is also the difficulty of research.
We wore the equipment for Beijing Swift in 2014, and in 2015, when Beijing Swift flew back to the Summer Palace again, we recovered the first batch of equipment.
This is one of the reasons why it took us 8 years to publish the paper, because a certain amount of data must be accumulated.
Due to individual differences, some of the 66 swifts wearing the locator did not return to the Summer Palace, some may have died of natural causes, and some we did not catch, and finally the data of 25 swifts were recovered.
Beijing News: Is it difficult to capture swifts wearing locators in the Summer Palace?
Liu Yang: Compared with Zhengyangmen and other places where swifts breed and carry out research in Beijing, the buildings in the Summer Palace are not very tall, so it is more convenient for us to operate.
Every time we capture, we have to deploy the net at two in the morning. When it was just dawn, the swifts flew out from the Kuoru Pavilion. Due to the poor light, they would hit the net. After we caught it, we checked whether it was wearing a locator. .
When the tourists entered the park one after another at 8:00 in the morning, our operation was completed.
The reason for the stopover may be "supply" or "waiting for the wind"
Beijing News: Are the 25 individuals representative?
Liu Yang: We have accumulated data on 25 Beijing Swifts in 4 years. In the study of migratory birds, this amount of data is relatively sufficient, so our article was published in authoritative journals.
During the migration process, the individual Beijing swifts are different, which is also a common phenomenon in bird migration.
The 37 countries mentioned in the article are the countries covered by all Beijing Swift flights.
These data can represent the migration routes of a population.
Beijing News: This study found that Beijing Swifts have a long pause. What is the reason for their pause?
Liu Yang: The stop mentioned in the paper, the stopover used in English, does not mean that it stops at a certain position and does not move, but that it stays in a certain area for a long time during the long migration process. As for Swift, it is shown as lingering in a local range.
We speculate there are two reasons: one is that the local food is very rich, they stay for a period of time for food replenishment and accumulate fat suitable for long-distance migration; the second is to wait for more favorable climatic conditions for flying.
Swift can fly at least 200 kilometers a day. On the one hand, it is due to its body structure. Its wings are long and narrow, and its body is streamlined; on the other hand, it is very good at using the wind to fly by the wind, which can reduce the flapping of the wings without too much effort.
The genetic code behind migration will be deciphered in the future
Beijing News: Why did you choose Beijing Swift as the research object?
What is the significance of this study?
Liu Yang: Before 2015, the migration route of Beijing swifts was unknown.
Some speculate that after leaving Beijing, they will fly over the Himalayas to the Indian subcontinent, while others believe they have flown along China's eastern coast to Southeast Asia.
On the other hand, the Beijing Swift is a wild migratory bird named "Beijing" and is one of the symbols of the capital's culture.
Beijing attaches great importance to the protection of Beijing Swift.
Everyone hopes that the population of Beijing Swifts will stabilize and even grow.
To protect a bird, you must first understand its behavior.
They breed in Beijing, where will they fly in winter?
Its migration path is what we need to figure out.
Beijing News: In the future, what research directions will the scientific research team have?
Liu Yang: "How do organisms migrate over long distances" has always been a topic of widespread concern in academia, and it is also one of the 125 most challenging scientific questions in the journal Science.
How did Beijing Swift complete the migration of nearly 30,000 kilometers?
They don't have navigation, so why do they follow the same route every year?
The little swifts just born in Beijing have absolutely no experience in migration. How can they successfully fly to the wintering grounds in southern Africa?
From these perspectives, the Beijing Swift is an ideal species for studying animal migration and navigation.
At present, we have only tracked their migration phenomenon, and we will study the migration mechanism of Beijing Swift in the future.
The laws of biological evolution are hidden in its DNA code. In the future, we will use genome sequencing technology to decipher the genetic code behind the Beijing Swift migration miracle.
Beijing News reporter Zhang Lu