Breaking the cognition! A large number of migratory birds "bird flow" actually fly horizontally across the Taklimakan Desert

Produced by: Science Popularization China

Author: Ma Ming (Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences)

Producer: China Science Expo

As autumn approaches, we welcome October 12th, International Migratory Bird Day. This is a day to raise public awareness of migratory bird protection, and it is also an important moment for us to reflect on the harmonious coexistence of humans and nature.

Migratory birds, these natural travelers, cross thousands of mountains and rivers with their amazing migration ability, connecting every corner of the earth. Their story is not only one of the most spectacular scenes in nature, but also an epic of survival.

To this end, we have planned a series of three articles on migratory birds, which will provide you with relevant scientific knowledge from two perspectives: the migratory routes of migratory birds and the scientific methods of tracking and investigating migratory birds (among them, scientists' tracking and investigating migratory birds are divided into two parts, and this part is about the migratory routes of migratory birds).

May you gain something from International Migratory Bird Day!

There are three major migratory areas for migratory birds in the world, including different migration routes

Birds' migration routes and flyways are both large-scale geographical concepts.

We can imagine a migration route as a wide corridor, a relatively fixed path that birds take when migrating between their breeding and wintering grounds.

The migratory area refers to the specific geographical area that migratory birds pass through during their migration, including one or more migratory stopovers on their migratory journey, which are "stations" where they stop to rest and replenish energy during their long-distance flights. These migratory stopovers are like bridges connecting the breeding grounds and wintering grounds of birds, helping them complete the entire migration process.

Geographically, the world can be divided into three major migratory bird flyways, namely the Asia-Pacific Flyway, the African-Eurasian Flyway, and the North and South American Flyway. These flyways include different migration routes. The species and numbers of birds vary on different migration routes, and there is a lot of overlap between routes. Therefore, a migration route does not refer to a precise path.

The migration routes of most birds are basically north-south, but birds that use different flying methods have slightly different migration routes, so east-west migration may also occur.

At least three migratory routes of migratory birds in the world intersect in Xinjiang

The sky is high and birds fly freely. Geographically, my country is located in a key position on the world's migratory routes for migratory birds from north to south and from east to west, and plays the role of a transit station.

Among the nine migratory routes for migratory birds in the world, four are closely related to the migration of birds in my country (Figure 1), namely: the Siberia-East Asia-Australia route, the North Asia-India (South Asia) route, the West Asia (Central Asia)-East Africa route, and the Western Pacific route.

Figure 1 Nine major migration routes (major corridors) of migratory birds around the world

(Image source: Nature 2014)

Among them, at least three international migration routes (major passages) pass through Xinjiang: the first is the West Asia-Middle East-East Africa route; the second is the Siberia-Central Asia-South Asia route; and the third is the Arctic tundra-Central Asia-Australia route (Ma Ming/Zhao Xumao, 2015). The northern Xinjiang wetland (spring overflow zone) has a unique geographical location and is located at the node of the three major international migration routes. Its important role in tracking and studying migratory birds is self-evident.

What are the migration patterns of migratory birds in northern Xinjiang?

1. The migration direction is mostly east-west;

In the northern part of the Tianshan Mountains in Xinjiang, due to the obstruction of high mountains and deserts, the direction of bird migration is not all "south to north", but is mostly consistent with the wind direction and the direction of the mountains - migrating in an east-west direction along the lakes or rivers in the northern part of the Tianshan Mountains, such as the Ili River, Irtysh River, and Ulungur River.

In the Junggar Basin, bird migration is blocked by the Gurbantunggut Desert and the Tianshan Mountains. Some birds bypass the Tianshan Mountains and fly westward or eastward; others follow the Urumqi River Valley or the Urumqi River Gorge to the Dabashan Pass and cross the basin between the Tianshan Mountains.

2. There are two obvious peak seasons: spring and autumn;

Bird migration in the Grand Canyon (including wetlands around Urumqi and other lakes) has two distinct peaks in spring and autumn, and the population reaches its maximum during the migration season.

In spring, migratory birds are eager to go north to find and occupy breeding grounds. They are in a hurry, traveling day and night and their stay is short.

In the golden autumn season, migratory birds from the northern breeding areas will pass through the wetlands on their way south, rest and replenish their energy, and wait for the right time (climate, moon phase, temperature, air flow) to migrate south. Their numbers increase faster and their stay time is longer, especially from September to October.

3. Bird activities vary with seasons and in the morning and evening;

The activity patterns of wetland birds vary with the seasons and the morning and evening. Many birds choose to migrate at night to avoid natural enemies. Birds like to come out to forage at dawn and dusk, and generally have two obvious peaks in the morning and evening in summer. As the seasons and temperature change, the daily rhythm changes, and the double peak phenomenon changes. For example, in winter, birds will have multiple activity peaks in order to replenish heat.

Even birds of the same species may stay for different lengths of time and take different migration routes. For example, some birds cannot migrate together because the female and male birds have different wing lengths.

4. Migration routes are different in spring and autumn;

In terms of spatial changes, northern Xinjiang is the breeding area for some birds, and all the way north, including the Altai Mountains, Siberia, and the Arctic tundra, are all bird breeding areas.

Most birds migrate north to breed in spring, and will stop temporarily in the desolate northern Xinjiang. In autumn, after breeding, birds migrate south with their families, and will stop for a while when passing through the Urumqi wetlands to replenish their energy and accumulate fat for the winter. In September or October, they will choose the right time to continue flying south to wintering grounds in South Asia, East Africa, Malaysia, Oceania, etc.

Urumqi is neither an ideal breeding ground nor a comfortable wintering place. There are very few resident birds in the area, only 40-60 species.

As to why some migratory birds have different migration routes in spring and autumn, there are different explanations and it remains a mystery.

Breaking the cognition: Some migratory birds will directly cross the Taklimakan Desert

Birds usually migrate along valleys, rivers, lakes, oases or coastlines. The Taklimakan Desert, China's largest desert, is vast and arid, and has always been considered a forbidden zone for life, with few reports on birds. However, in the past three decades, the author has conducted field surveys in the heart of the desert many times, and has recorded the activities of birds during each crossing of the desert.

The author participated in the comprehensive survey of the Taklimakan Desert, the Lop Nur survey, the Kunlun Mountains-Karakoram Mountains comprehensive survey, the China-Japan desert hiking expedition and the desert crow survey organized by the Hong Kong Bird Watching Club, and recorded the activities of resident birds, wintering birds and migratory birds (migratory birds) in the heart of the Taklimakan Desert or the Lop Nur Desert.

In spring and autumn, a large number of "bird flows" cross the 600-800 km wide desert, including some small birds weighing only 8 to 10 grams.

It is generally believed that birds' routes across the desert are inseparable from oases and rivers. It has been confirmed that the Tarim River, Hotan River, Yarkand River, Cherchen River, Ili River, Kaidu River, etc. are all important channels or stations for bird migration.

However, through surveys conducted in the center of the desert, the results show that many species of birds also appear in the desert hinterland far away from rivers and oases. According to the characteristics of the flora, the following types are divided:

(1) Indigenous species (resident birds), that is, birds that live in the desert all year round. According to observations, there are resident birds in the heart of the desert, but the number is very small. The recorded species include white-tailed crows, short-toed larks, black-capped sparrows, etc. The hairy-legged sandgrouse and desert grouse often move between the desert and the Gobi, and also appear in the heart of the desert.

White-tailed crow in the Taklimakan Desert

(Photo source: Huahua's paintings)

(2) Companion species: With the rise of the oil industry, people have built many settlements in the desert. These settlements have created conditions for bird life and have become new territories and refuges for many oasis birds. Companion species actually include resident and migratory birds that live on the edge of the desert, such as shrikes, sparrows, gulls, doves, etc. There are also some lost birds and winter migratory birds.

(3) Passenger species (migrant birds), accounting for 78% (Ma Ming et al., 2000).

(4) Lost species (lost birds), including some wandering species, such as the waxwing, blackbird, red-necked thrush, black-throated thrush, etc.

Observations have confirmed that about 84 bird species from 10 orders and 25 families appear in the heart of the desert (Ma Ming et al., 2000). Among them, 22 species of waterfowl account for about 26%, and 50 species of small passerines account for about 59.6%. About 78% of the species are passing species, and the rest are companion species or lost species.

Conclusion

Xinjiang is a paradise for studying and observing migratory birds. However, these migratory birds travel long distances and migrate all over the world, which greatly increases the difficulty of scientists' observation. Do you know how scientists track and investigate them? There are many stories worth sharing. Please pay attention to the next two articles in this series~