Question

do you agree with the frog's assessment that the nightingale is a brainless Bird

Answer 1

No, i don't think that the nightingale is brainless. Being simple, shy or dismissive does not mean that youbare foolish. She wanted to be successful and placed singer. So she accepted the frog's advice of giving her a vocal training. Her only fault was that she lacked confidence.
Hope this will be helpful :)

Answer 2

Yes , I think the Nightingale is brainless because firstly she believed the frog that the owned sumac tree and he was a splendid singer. She didn't once think that he could be lying. She didn't ask him to sing or compare with him . In fact she began thinking very highly of him. She was a fool to have let him earn money by selling her songs for silver. The Nightingale practiced and sang against her wishes. She was not sensible enough to refuse the frog for any of his unreasonable demands and persuasion. She did not once think of finding a solution or flying away when she was not happy. So the frog's assessment that the Nightingale is a brainless is absolutely right.

I hope this will help u :)