Theory:

     But one day when Princess September went to say good morning to her parrot she found it lying dead at the bottom of its golden cage. She burst into a flood of tears, and nothing that her Maids of Honour could say comforted her. She cried so much that the Maids of Honour, not knowing what to do, told the Queen, and the Queen said it was stuff and nonsense and the child had better go to bed without any supper. The Maids of Honour wanted to go to a party, so they put Princess September to bed as quickly as they could and left her by herself. And while she lay in her bed, crying still even though she felt rather hungry, she saw a little bird hop into her room. She wiped her tears and sat up. Then the little bird began to sing and he sang a beautiful song all about the lake in the King’s garden and the willow trees that looked at themselves in the still water and the goldfish that glided in and out of the branches that were reflected in it. When he had finished, the Princess was not crying any more and she quite forgot that she had had no supper. “That was a very nice song,” she said.
Explanation:
 
Princess September went to say "Good morning" to her parrot one lovely morning. She was heartbroken when she discovered the bird dead at the bottom of the golden cage.
 
The little princess cried uncontrollably as she realised she had suffered an incredible loss. The Maids of Honour attempted everything they could to console her, but it was fruitless.
 
4.jpg
A sobbing child
 
The Maids of Honour, unable to console the Princess, decided to forward the message to the Queen. After hearing the Maids of Honour, the Queen pronounced the situation to be "stuff and nonsense." She then directed the Maids of Honour to send the child to bed hungry.
 
The Maids of Honor, on the other hand, had a party to attend. As a result, they hurriedly put September to bed and abandoned her. However, the Princess had not slept. She was weeping even though she was hungry. At that very time, she noticed a little bird fly into her room.
 
When the Princess saw the unusual activity, she dried her eyes and sat on the bed. The tiny bird suddenly erupted into a lovely song. He began singing about the lake in the King's garden, then about the willow trees that mirrored in the calm water and the goldfish that floated in and out of the reflected branches.
 
What had occurred had captivated the Princess. She had stopped sobbing and had forgotten about her lack of food. Finally, she acknowledged that it was a charming song.
 
In this portion of the story, the Queen mother does not heed the child's grievances, displaying her careless attitude towards her child. Instead of being supportive, she dismisses her child's state of mind as mere foolishness. On the other hand, the Maids of Honour exhibit negligent behaviour too. Instead of being by the side of the mourning child, they set out to party. Defying the Queen's orders, the Maids of Honour does not even put the child to proper sleep.
 
According to Somerset Maugham's original title, "Princess September and the Nightingale", the bird that visits the princess' chamber is a Nightingale, a songbird.
 
Nightingales are migratory birds that one may find across Europe and Africa.
 
In popular literature, Nightingales are often regarded as an object of symbolism. The Nightingale is widely seen as a spring signal, with its song bringing in new leaves after the winter.
 
Similarly, in this story, the Nightingale uplifts the mood of the otherwise grieving Princess, like spring after a gloomy winter.
 
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A nightingale
 
Meanings of difficult words from the paragraphs:
 
S.No
Words
Meanings
1
Maid of honourThe most important bridesmaid at a marriage ceremony, but in this context, maids of honour are the ladies aiding the Princess
2
Stuff and nonsenseA phrase used to indicate that you believe something is untrue and/or ridiculous
3
SupperA light meal consumed in the late evening before retiring to bed
4
GildedTo cover a surface with a thin layer of gold or a substance that looks like gold
5
Willow treesTrees that usually grows near water and has long, thin branches that hang down
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.