The prototype of the king in the night is actually an amazed expression pack! !

Beijing Temple of Heaven Park is an important habitat for wild birds in Beijing, and an important place for them to mate, breed, build nests and forage. Since 2003, a total of 166 bird species have been recorded in the Temple of Heaven Park, including resident birds, migratory birds and migratory birds. The long-eared owl we are going to introduce today is a winter migratory bird.

World Migratory Bird Day is held on the second Saturday of May and October each year. Related activities are aimed at enhancing public awareness of protecting migratory birds and their habitats. Today, taking the opportunity of World Migratory Bird Day, let's learn about long-eared owls and protect these lovely creatures~

Image source: ebird

Walking exclamation expression pack

Xiao (鸮) is a general term used by ancient Chinese to refer to owls. The long-eared owl is a typical species of the genus Ostrachniidae, and is one of the most widely distributed and numerous owl species in the world. Owls in the same genus are usually called eared owls, including long-eared owls and short-eared owls. Although they have many similarities and belong to the same genus, they actually diverged very early, so the genetic correlation between the two is not strong.

Short-eared owl resting under a tree

Image credit: Sumeet Moghe

As the name suggests, long-eared owls have long "ears", which are actually a tuft of feathers similar to the ears of mammals. Half of the existing owls have ear tufts, but the tufts of feathers of other owls are very short and almost difficult to find on their round heads. Only the two tufts of feathers of long-eared owls point straight up like exclamation marks, which makes them look like an exclamation expression.

Image source: Xianwei Zeng

The purpose of ear tufts is still unclear, but most biologists and ornithologists agree that ear tufts may be a way to identify characteristics and express emotions within the population. It also has a certain warning function. The ear tufts are usually in a "lying down" state. When frightened, the long-eared owl will erect them. The short-eared owl will also show its ear tufts when it is in a defensive posture, but it is almost invisible.

Long-eared Owl with folded ear tufts

Image credit: Tom Meaker / Alamy Stock Photo

It is worth mentioning that the long-eared owl has a special eating habit. It almost only eats small rodents, especially rats. In the Temple of Heaven Park at the beginning of the century, the long-eared owl liked to prey on rats, and to a certain extent played a role in controlling rodent infestation.

Hearing the invisible prey

Owls are the true kings of the night, and they have evolved unique adaptations to perfectly fulfill this role. For example, their characteristic large tubular eyes help owls see in near-total darkness, and their extraordinary hearing system allows them to operate in complete darkness. Even their iconic large face is key, as they have special feathers on their face that direct sound to the external ear openings, helping with sound localization, similar to the human outer ear.

Image source: USFWS Mountain-Prairie - Long-Eared Owl on Seedskadee NWR, Public Domain

Most owls use a combination of excellent vision and hearing to hunt prey, but the Long-eared Owl has a further auditory system that allows it to locate prey that is completely invisible to the naked eye, whether it is hidden in dense vegetation or beneath a thick layer of snow.

Such "abnormal" hearing is due to the asymmetric ears of the long-eared owl, which makes the high-frequency hearing and sensitivity between the two ears different in the vertical direction, and there is a time difference in the distance of the two ears receiving the sound. During the flight, the up and down movement will cause a level difference between the two ears of the long-eared owl, that is, the interaural level difference (ILD). At this time, the sound source will form an elevation angle with its position. If it is at the same height, the elevation angle is 0°.

Long-eared owl gill cover

Image source: Creative Commons

Generally speaking, the left ear is slightly higher than the right ear, so sounds from below sound louder in the left ear, and sounds from above sound louder in the right ear. By measuring the difference in sound levels reaching each ear, the long-eared owl can tell whether the prey is above or below.

In addition to the elevation angle, the long-eared owl can also determine the horizontal angle. Whenever a sound source occurs, it can locate its source through the slight time difference between the left and right ears. For example, if the sound is produced on the left, the left ear will hear the sound before the right ear, and then the long-eared owl will turn its head until the sound reaches both ears at the same time, thereby locking the direction of the prey. At the same time, there will be a time difference of the shortest one millionth of a second between the two ears, that is, the interaural time difference (ITD). At this time, the sound source will form a horizontal angle with its location. If the sound source is facing the face of the long-eared owl, the horizontal angle is 0°.

Image source: allaboutbirds.org

Therefore, the long-eared owl can obtain the position and height of the prey through the interaural level difference (ILD) and interaural time difference (ITD). In the brain, these two systems are processed independently in independent neural pathways and converge the sound information to the outer nucleus of the hypothalamus to form a spatial auditory map.

Life is not easy, owl sighs

As a predator that relies on hearing to survive, the "harm" caused by human noise to the long-eared owl is no less than the spiritual pollution brought to us by brainwashing songs such as "Dig, dig, dig..." and "Love is like fire that warms the heart..."

A paper published in Acta Zoologica Sinica in 2018 revealed the impact of noise and the presence of urban infrastructure on the distribution of owl nests. The results showed that with the rapid growth of the human population, the original habitats of long-eared owls - forests and grasslands - are gradually being encroached upon, and the noise pollution brought by humans has "paralyzed" their sensitive auditory systems. After hearing too many noises in one night, they did not catch any prey, but almost suffered from neurasthenia.

Image source: Owl Research Institute

This causes their hunting efficiency to drop rapidly in areas with high environmental noise levels, forcing them to abandon their original breeding grounds or habitats that appear to be good.

For example, there used to be nearly a hundred long-eared owls in the Temple of Heaven Park, but now only a few migratory individuals can be seen passing by.

Of course, noise is not the only dilemma faced by long-eared owls. In high-latitude areas, some long-eared owls even begin to forage during the day. The reason is probably due to the tight food resources and difficult life. The owl sighs.

References:

1. Jin Heng, Li Qiang, Chen Jiao, et al. Survey of bird resources in Temple of Heaven Park[J]. Journal of Beijing Agricultural College, 2022(002):037.

2.Long-eared-owl

https://en.wikipedia.org/wiki/Long-eared_owl

3.Designed for Darkness: The Unique Physiology and Anatomy of Owls

https://www.intechopen.com/chapters/80275

4.Noise shapes the distribution pattern of an acoustic predator

https://doi.org/10.1093/cz/zox061

Author: Fish

Winner of the Silver Award for Outstanding Science Popularization Works of China Science Writers Association

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Editor: Guru