Theory:

      “Don’t be such an old silly,” said September. “I’ve put you in the cage because I’m so fond of you. I know what’s good for you much better than you do yourself. Sing me a little song and I’ll give you a piece of sugar.”
 
     But the little bird stood in the corner of his cage looking out at the blue sky, and never sang a note.

     “What’s the good of sulking?” said September. “Why don’t you sing and forget your troubles?”

     “How can I sing?” answered the bird. “I want to see the trees and the lake and the green rice growing in the fields.”

     “I’ll take you out every day,” she said.

     “It’s not the same thing,” said the little bird. “The rice-fields and the lake and the willow trees look quite different when you see them through the bars of a cage.”
Explanation:
 
September declared the bird's plea as foolish. She said that she had entrapped him because she adored him. She also stated that she was conscious of what was best for him. She then requested that he perform a short song in exchange for a piece of sugar.
 
The tiny bird, on the other hand, never attempted to sing. He stood in the cage's corner, staring out at the beautiful sky. September then questioned the bird's sad demeanour. She recommended he perform a pleasant song to brighten his spirits.
 
The bird said he would need to be in the natural world before even trying to sing. He stated that he would need to view the trees, the lake, and the green rice growing in the fields in particular.
 
Every day, the Princess volunteered to take the bird out for a walk. However, the bird did not appear to be interested in the concept. He didn't think his needs and her idea were the same. The rice fields, lake, and willow trees, according to the bird, would appear entirely different through the cage bars.
 
Meanings of difficult words from the paragraphs:
 
S.No
Words
Meanings
1
SulkingA period of time when someone refuses to smile or be pleasant because they are angry about something
Reference:
National Council of Educational Research and Training (2008). It so happened. Princess September - Somerset Maugham (pp. 34 - 44). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.