It looks like the USPS got this very wrong. The stamp enshrines a misattribution.
Quote on Angelou stamp apparently came from another author
WASHINGTON — The U.S. Postal Service issued a new limited edition “Forever” stamp Tuesday, honoring the late poet, author and civil rights champion Maya Angelou, but it carries a quote that apparently originated elsewhere.
Angelou rose from poverty, segregation and violence to become a force on stage, screen and the printed page. She died last May at her Winston-Salem, North Carolina, home at 86.
The stamp dedicated Tuesday at a Washington ceremony showcases Atlanta artist Ross Rossin’s 2013 portrait of Angelou, an oil painting in the Smithsonian’s National Portrait Gallery collection.
The stamp includes the quotation: “A bird doesn’t sing because it has an answer, it sings because it has a song.”
Children’s book author Joan Walsh Anglund told The Washington Post (Book author Joan Walsh Anglund says of Angelou stamp: ) the quotation is in her book of poems “A Cup of Sun,” published in 1967. Anglund, 89, said she didn’t know about the stamp but that she hopes it is successful. . . .