On the same day, the Red Star News reporter called China Eastern Airlines customer service, the direction of the reporter confirmed that the flight has returned. When asked about the reason for the return flight, the customer service said that she had found on the system that the external reason for the release at 20:37 was the airport flow control. However, the reason for return may be updated later. About 45 minutes later, the Red Star News reporter called China Eastern Airlines customer service again. Another customer service said that the reason for the flight’s return had been updated to “external reasons”, and more specific contents could not be seen. Recently, according to a paper published in the journal ecology and evolution, scientists from the Norwegian Institute of Natural Sciences (Nina) have found that a small change in the wind turbine can “bring new life to birds”. By painting one blade of the turbine black, the researchers reduced bird deaths by more than 70% in three years. < / P > < p > this news has attracted netizens’ comments: how bad is the bird’s eyes? Not only do birds often hit airplanes, but even wind turbines several stories high can head-on. In fact, birds can surprise all doubters if they want to compete for sight – after all, if Eagles want to catch chickens, they have to see them first. Dinosaurs, the ancestors of birds, dominated the earth’s continent in ancient times. At the same time, the ancestors of mammals lived in the ground, or lived a nocturnal life, so vision gradually degenerated. In fact, there are four kinds of cone cells in the retina of vertebrate common ancestor (they are photoreceptors of different colors) and “see” the world through these four independent photoreceptors. But in viviparous mammals, there are only two types of cone cells left, which cannot subdivide long wavelength visible light and short wavelength ultraviolet light. < / P > < p > by about 30 million years ago (the dinosaurs were extinct), one of the original two photoreceptors produced a mutant in one of the primate ancestors, restoring the ability to distinguish red and green. However, the newly acquired photoreceptors have poor resolution and uneven distribution in the retina. Therefore, there are three kinds of photoreceptors in the retina today, which mainly absorb red, green and blue visible light. Primates see more color than mammals, such as dogs, that still have only two types of cone cells. < / P > < p > current studies have found that most birds have UV vision. Help them find food and mates. For example, a fruit with a waxy rind reflects more ultraviolet light, allowing birds to distinguish from a distance. Some flowers will present more complex patterns under ultraviolet light, which attract hummingbirds, bees and other animals with ultraviolet vision. < / P > < p > in addition, just as some pet owners can judge whether their pets are defecating around the house through ultraviolet light, wild birds of prey can also see traces of urine left by rodents in the sun. Birds are the most colorful group in the animal world, and some birds with monotonous coat color and difficult to distinguish male and female for human beings have different feather textures under ultraviolet light. Compared with birds, human beings are “UV color blind”, which is a whole dimension different from them in vision. < / P > < p > based on the discovery that birds have UV vision, scientists have developed a variety of products, such as glass with stronger UV reflection and cat collar, which can cause birds to be alert and reduce unnecessary bird death; clothing materials with less UV reflection are suitable for bird lovers to hide themselves. However, if you can’t find the north, you will be in trouble. Scientists have discovered that cryptochrome, a type of photosensitive protein in the eyes of migratory birds, generates tiny electric charges and senses the earth’s magnetic field. Do these birds perceive the earth’s magnetic field through vision or a sixth sense? It is not known yet. < / P > < p > the eyes of birds account for about 15% of the head weight (the eyes of birds of prey are 1.4 times of those of other birds of the same size), while the eyes of humans only account for about 1% of the head weight. A larger eye is like a telescope with a larger aperture, which can collect more light. Early bird, active after sunrise, often has larger eyes than those that sleep in. < / P > < p > birds’ eyes are not nearly spherical like humans, but a flat bell shape. The flatter eye structure, together with a more forward lens, increases the projection on the bird retina. In addition to stretching the lens, birds can change the focus by adjusting the curvature of the cornea. Around the eyes, there is a special bone structure called “sclera ring”, which is composed of more than 10 small bones, each of which is connected with muscles to help birds quickly change their focus of attention. Compared with mammals with clever eyes, the eyes of birds are relatively fixed in the orbit and appear sluggish. In fact, birds not only have big eyes, but also have more gods (Scriptures): on the retina of human beings, there are about 200000 photoreceptors per square millimeter. In contrast, the density of photoreceptors on the retina of domestic birds with ordinary vision is 400000 per square millimeter, and that of raptors is more than one million. At the same time, birds transmit more visual signals in ganglia, which means the “pressure” of visual signals On the contrary, the shrinkage rate is lower than that of human beings and other animals. The photoreceptor cells of human retina are mainly located in the fovea. When we look at an object, the light from the object is focused on the fovea of the fundus macula with the highest resolution. The image without focusing on the fovea is “residual light”, and the resolution is not high. In addition to nocturnal birds, most birds have multiple structures similar to the fovea of the human eye, even connected in a band. < / P > < p > blood vessels in the human retina can interfere with vision to some extent. Most birds have a specialized vascular system called “comb membrane” in the retina, which not only reduces glare, but also provides them with more sensitive motion detection capabilities. The faster “camera refresh rate” makes birds more adaptable to travel through the leafy forest. According to the human eye’s ability to respond to 24 frames per second, only a blur of the surrounding environment can be seen when moving rapidly (for some extremely fast courtship dances, scientists have to use high-speed cameras to distinguish them). < / P > < p > in addition, birds (and modern reptiles) have another visual superpower – fat droplets in their cones. These droplets not only protect against UV damage, but also act as miniature prisms to help light focus on photoreceptors. According to the type and concentration of carotene, the color of these fat droplets will also be different. < / P > < p > these small “pixel filters” further enhance the color discrimination ability of birds. For example, many seabirds can see the misty distance with the help of these red and yellow droplets. < p > < p > the American tea Falcon can distinguish insects 2 mm above the ground at the top of a tree 18 meters high. As sharp as a bird, why do you bump into a huge wind turbine? The collision data mastered by scientists actually reflect the visual world of different birds. The study found that birds that are prone to colliding with high-voltage wires are often those with eyes on both sides of their heads – a wider angle of view (for example, pigeons, parrots and other binocular views of about 300 degrees) helps them avoid natural enemies and fly in complex environments, but they may have blind spots in front of them. On the other hand, the birds of prey, such as hawks and falcons, can better see the depth of field and the distance of objects, but the angle of view is smaller. They tend to pay too much attention to the prey on the ground and ignore the obstacles in front of them. Some birds have eye structures that are more adaptable to flight, able to see both the ground and the distant horizon at the same time, but at the cost of not being able to judge what is close at hand. In fact, according to the different living environments of birds, their visual systems have adapted and compromised. For example, penguins adapt to diving, the cornea becomes flat, and the lens muscles become very strong; owls have a large number of “rod cells” with high photosensitivity, while few cone cells can distinguish color. In addition to owls, most birds have poor night vision ability, and their habits are also ambush in the daytime and emerge at night. Even so, some birds migrate at night and crash into man-made buildings with poor eyesight. < / P > < p > even in the daytime when there are plenty of optical fibers, glass, a man-made material, may be too unfamiliar to birds. Some trained birds can distinguish glass, but wild birds don’t have a chance to make a mistake. The word “bird’s-eye view” describes a commanding perspective. This view can be easily obtained by birds, but many land animals can only achieve it by climbing. Obviously, we have not yet reached the top of the mountain for our understanding of bird vision. Didi Qingju bicycle has entered 150 cities