The correct answer should be: "It is part of Chapter Nine, called 'IT'".
Explanation:
It is important to highlight that the number of the pages are always dependent on the version and edition used! For this answer, the version of the book in pdf file available for free on the internet and easily found provides the number of the page where the quote can be found in page 70. Anyways, the book "Wrinkle in Time" was first published in 1962 by its author Madeleine M'Engle. The passage quote comes from Chapter Nine, called "IT", in which the characters are reflecting upon a discourse about equality.
I believe that the thrush's song changed the mood because it was a song filled with hope from the divine that inspired him. Darkling Thrush refers to a bird who is weak and fragile, however, even with these qualities, he sacrificed himself.
