Hire birds to check the weather for us

 　　In Chinese folk proverbs, there are many examples of animals being able to carry out weather forecasts, such as "frog croaks, heavy rain arrives", "fish jumps out of water, wind and rain arrives", "bees return late, good weather comes", all of which reflect The care and wisdom of the working people. However, it used to be just a matter of luck, after all, people couldn't watch what the animals were doing all the time. In modern times, people can really "hire" animals as weather forecasters, and the first animals to be hired are birds.

Across the ocean, a piece of cake

　　We know that many birds have the habit of migrating, sometimes over long distances. If it's on land, it's fine, and the birds can stop for food and rest at any time. What if they want to fly across the ocean? So for a long time, it was believed that only seabirds and small birds could fly across the ocean, and large land birds could only travel short distances of less than 100 kilometers. But recently, a study overturned that notion.

　　Researchers at the Max Planck Institute for Animal Behaviour in Germany used GPS technology to track the ocean- and sea-crossing behavior of 65 birds from five different species, and found that most of these land birds can fly over the ocean in one breath. Fly hundreds or even thousands of kilometers. How do they do it? It turns out that they are very good at using the help of the wind. With the help of tailwinds and thermals, land birds can fly quickly across the ocean in the most energy-efficient way, so that they don't have to worry about the problem of "poverty" at sea.

　　The research team analyzed the ocean-crossing routes that 112 birds tracked in the past may have used to determine the criteria for the birds to choose the ocean-crossing route. They found that the wind direction has a great influence on the route choice of birds, and as long as the wind is guaranteed, they rarely consider the length of the journey and food supply. For example, when the eastern honeythrush migrates from Japan to Southeast Asia every year, it will fly 700 kilometers above the East China Sea. In order to choose the best departure time, they need to constantly observe the changes in airflow and wind direction, and choose the day when the wind direction is most conducive to migration. Then take a long-haul flight of up to 18 hours. Also, they use the rising thermals to fly higher on their journeys, and proper lift means less drag, so less energy is expended on the journey across the ocean.

　　The secret of birds' easy ocean crossing is precisely because they can accurately predict the airflow and wind direction over the Pacific Ocean.

Why do birds sense airflow

　　Anticipating changes in airflow is not an easy skill to acquire. How do birds learn it?

　　Birds have modified many body parts for flight, one of which is the skeleton. Unlike most vertebrates, the main function of a bird's skeleton is not to support, but to adapt to flight, so its skeleton develops in the direction of "thinness" and "healing". A bird's skeleton makes up only about 5% of its body weight, while a human skeleton makes up 20% of its body weight. The bones of birds are mostly hollow and brittle. There is no bone marrow in them, but they are filled with air. Most of the bones are connected as one, reducing unnecessary movable joints, which is conducive to weight loss and balance in flight.

　　This change in the bird's skeleton causes its internal pressure to be basically the same as the atmospheric pressure. Once the atmospheric pressure changes, the bird can immediately perceive it. For example, before a rainstorm comes, the air pressure decreases, and birds can feel this subtle change through their bones. Seabirds are the most adept at taking advantage of this, as they seek land to avoid storms on the eve of a storm at sea. Sailors use this nature of seabirds to predict storms and ensure safe navigation.

　　Birds' ability to sense air currents may also stem from their excellent hearing, which allows them to hear the whistling sound of an approaching wind and rain—infrasound—over great distances. In 2014, American scientists recorded a bizarre migration. A group of golden-winged warblers, which had just flown 5,000 kilometers from Columbia to eastern Tennessee two weeks ago, started their long-distance migration. They flew to a place 700 kilometers away in one go. off the coast of Florida, and one flew as far as Cuba. Why do birds travel long distances so painstakingly, do they fall in love with the feeling of free flight? Only two days later, the mystery was revealed. A huge storm hit Tennessee, causing serious casualties and economic losses. The golden-winged warbler who "fleeed" in advance successfully avoided the disaster.

　　This time, it wasn't changes in air pressure that helped the birds predict airflow and avoid disaster. The researchers examined factors such as air pressure, temperature, cloud cover or rainfall that predict changes in weather, and found no significant fluctuations in any of these factors. From this, the researchers hypothesized that the golden-winged warblers sensed the storm two days earlier because they heard the infrasound waves produced by the approaching storm. The infrasound waves produced by storms can travel thousands of kilometers, and the birds are warned by the infrasound waves, so they run away.

Recruiting Bird Weathermen

　　Birds, it seems, are much better at predicting weather than humans, and they can easily know the exact path of a storm several days in advance, while our weather experts may still be digging in. So, can we use this ability of birds for us?

　　Ornithologist Frederic Gigue at the French National Museum of Natural History and his team are "training" a group of ornithological meteorologists to see if birds have indeed developed a set of warnings for storms or tsunamis at sea , whether people can predict these disasters by identifying the behavior of birds.

　　Researchers bound 56 birds from 5 species with state-of-the-art animal trackers that can transmit the birds' positions to the International Space Station, which in turn feeds data back to scientists on Earth for scientists to use Follow the birds as they forage, migrate and rest while waiting to see how these birds respond to natural disasters. If the previous conjecture is correct, the researchers expect they will also observe unplanned migrations by birds to avoid storms or tsunamis.

　　Researchers need to summarize how the birds sense weather changes and whether they can learn from their sensing methods to develop early warning systems. Of course, if you don't learn how to come to birds, humans can also judge whether a disaster is imminent by observing the migratory behavior of birds. However, if direct observation is to be used, in order to ensure the accuracy of the warning, one may need to adopt a "wide-casting net" strategy - the team plans to relocate hundreds of birds across the Pacific Ocean for potential tsunami warnings Prepare. So far, there are still many variables and difficulties in weather forecasting. If we can learn from the advanced experience of animals, this work may be more effective with less effort. Let us learn from bird weathermen.