Symbolism, Imagery, Allegory
The title of the book is To Kill a Mockingbird, so mockingbirds must be important, right? But why? Let’s look at a few passages to try to figure out some answers to that question.
Mockingbirds first appear when Jem and Scout are learning how to use their shiny new air rifles. Atticus won’t teach them how to shoot, but he does give them one rule to follow.
Atticus said to Jem one day, "I'd rather you shot at tin cans in the back yard, but I know you'll go after birds. Shoot all the bluejays you want, if you can hit 'em, but remember it's a sin to kill a mockingbird."
That was the only time I ever heard Atticus say it was a sin to do something, and I asked Miss Maudie about it.
"Your father's right," she said. "Mockingbirds don't do one thing but make music for us to enjoy. They don't eat up people's gardens, don't nest in corncribs, they don't do one thing but sing their hearts out for us. That's why it's a sin to kill a mockingbird." (10.7)
So, mockingbirds are harmless, innocent creatures, and killing them is wrong, because they don’t hurt anyone. (The same could be said for cows, but hamburgers are so tasty, while mockingbirds presumably aren’t.) But is this lesson so important in itself that it’s worth putting it front and center on the cover of the book? There must be more going on here.
Mr. Underwood’s editorial after the death of Tom Robinson doesn’t mention mockingbirds by name, but it does have a similar message.
Mr. Underwood didn't talk about miscarriages of justice, he was writing so children could understand. Mr. Underwood simply figured it was a sin to kill cripples, be they standing, sitting, or escaping. He likened Tom's death to the senseless slaughter of songbirds by hunters and children, and Maycomb thought he was trying to write an editorial poetical enough to be reprinted in The Montgomery Advertiser. (25.27)
Mr. Underwood may be trying to get through to even the stupidest...