Theory:

The story was written by a writer Ruskin Bond. He was famous for his literary works in children's literature. The author narrates a fight between a cobra and a mongoose, which he had witnessed as a young boy while sitting atop a banyan tree at his grandparents' house. The banyan tree is older than the author's grandfather. While the banyan tree is the oldest, it is also the biggest tree in the garden.
 
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*Banyan tree
 
Even though the garden belongs to his grandfather, the banyan tree belonged to the author as grandpa couldn't climb the tree as he was sixty-five years old. The banyan tree has long branches which touch the ground, and they occupy a large space in the garden. The tree was as old as the city where it was planted - Dehradun. Small creatures like squirrels, snails, and butterflies were living on its branches. During summer, the boy enjoyed the company of the Banyan tree as not only did it serve as his reading spot, but also a hiding spot during times of need.
 
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Butterflies and snails

Our author became friends with a small grey squirrel. At first, the squirrel felt uncomfortable and tried to behave in a not-so-friendly manner with him. Usually, children used to harm small creatures with catapults, small toys made for shooting stones. When the squirrel found that the boy was not harming him, it became friends with the boy. The boy felt so happy, and he started bringing cakes and biscuits for the cute little squirrel. When the squirrel grew big and bold, it started searching for snacks by jumping into the boy’s pockets. The squirrel’s friends and relatives thought that the young squirrel was foolish for trusting a human.
 
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Squirrel

When the spring season began, the banyan tree started to produce small red figs. The tree branches were filled with different kinds of birds like the red-bottomed bulbul, parrots, myna, and crows. All these birds used to fight with each other on the branches. The sounds that all these birds made, turned the banyan tree into the noisiest place in the garden.
 
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Birds on branches

The boy made a primitive platform on the tree branch to sit and relax in the afternoons. He took a cushion from his living room, and he was leaning against the tree. And so, he could read his favourite books on the tree when the afternoon was not too hot. He also made a tree library with his favourite books like 'Treasure Island', 'Huckleberry Finn', and 'The Story of Dr. Dolittle'.
 
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Tree library
  
When the boy gets bored of reading, he could see down and look at the world below from the tree. The tree is so big and tall, and so the boy could see anything in a clear view. On one particular afternoon, the boy saw the classic fight between the mongoose and the cobra. He had the best possible view from his position on the tree, and it was the fight between two natives of the wild.
 
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The boy could see anything in a clear view
  
During the summer, there was a warm breeze and heat everywhere. It made everyone stay inside the house. The boy felt so tired and sleepy, and he was thinking of visiting the pond where he could enjoy a swim with his gardener Ramu and the buffaloes, when the boy saw a large black cobra moving smoothly and coming out from a bunch of cactus. Suddenly, a mongoose also came out from the bushes at the same time, and it went straight to the cobra.
 
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Cobra

When the sunshine hit the ground, both the cobra and the grey mongoose encountered each other under the banyan tree. The mongoose was three feet long, and an excellent fighter. The cobra knew that the mongoose is a wise animal, and it got itself ready to attack. But the cobra is also an equally strong fighter as it could attack the mongoose at high speed. And the speed of cobra is compared with the speed of light. The cobra has a hollow behind his long sharp tooth, and it is filled with a deadly poison. And so, this makes the cobra a strong attacker against the mongoose. Thus, it was a classic battle between the two champions in the garden.
 
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Mongoose

The cobra creates a hissing sound in defiance, and it moved the tongue quickly in and out. Then cobra rose itself from the ground and spreaded his hood to fight and attack the mongoose. Also, the mongoose showed his readiness to fight by brushing his tail and raising his fur.

The participants in the fight were not aware of our author's presence atop the tree but two other spectators, a myna and a crow were watching carefully. They witnessed everything and were settled on the cactus to watch the result. But they were not satisfied with just watching, rather they wanted to participate in the fight.
 
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Myna
 
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Crow

The cobra was trying to trap the mongoose with his false movements, but the mongoose was well aware of the power of its opponent. So he fixed his focus on attacking the cobra at a point just below the cobra's hood and started the attack.

The mongoose made false quick movements very close to the cobra. The cobra attacked and moved its hood down so quickly that it seemed the mongoose would not be saved. But this small creature was quick to jump and move on one side. It also bit the snake on its back and again moved away out of its reach.

The moment the cobra was attacked, the crow and myna threw themselves at him. When they flew towards the cobra, they hit each other. It must have been painful because they made loud noises at each other, and they went back to the cactus. Here, the boy perceives the noises made by the birds as insults; he feels that the birds were insulting each other for having collided. By using the phrase "shrieking insults", the boy has personified the birds.
 
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Birds collided

Drops of blood were shining on the cobra's back. And it was a strong hit by the mongoose.

The cobra was trying to attack the mongoose but missed it. The mongoose again jumped aside. The birds again tried to attack the cobra but collided with each other. So they went back safely to the cactus.

Third time again, the birds tried to attack the cobra in the same manner, but this time there was a change. They didn't collide with each other. The myna flew back to its shelter, but the crow tried to continue the fight in the air, and it swerved. In the second trial, the cobra also moved suddenly and attacked the crow with full force.

The boy noticed the crow falling twenty feet away. It kept shaking its body for some time, but then it became still and died. The myna was on the cactus, and she didn't interfere in the fight after the crow's death. The cobra was weakened and exhausted. The mongoose attacked fearlessly, when the cobra became tired of moving, the mongoose made a fast attack, showing his ability to assess the cobra's power accurately, and it turned it into his victory. Finally, the cobra was killed by the mongoose. It caught the cobra just below its hood and dragged it into the bushes.
 
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The mongoose dragged the cobra into the bushes

The myna rushed to the ground and hopping about she reached near to the bushes. Then, she flew away with a congratulatory squeal.
Reference:
*Banyan tree: By Kiran Gopi - Own work, CC BY-SA 2.5 in, https://commons.wikimedia.org/w/index.php?curid=15023516