You Know Why the Caged Bird Sings?

A single question can arise in different contexts, and have different answers. Here’s an example — a study and a book both written in the late 1960′s:

“The influence of vocal behavior on the performer’s testicular activity in budgerigars (Melopsittacus undulatus),” Barbara F. Brockway, The Wilson Bulletin (1967): 328-334.

and

I Know Why the Caged Bird Sings, Maya Angelou, 1969.