The character who is most like a mockingbird is Boo Radley.
Boo Radley is the quiet, reclusive neighbor of the Finches. He never leaves the house, after a run-in with the law as a youth. Most of the neighbors think he is crazy or dead, and Miss Stephanie Crawford believes he runs around at night peeping in windows. Kids won’t eat nuts from the Radley trees, because they think they are poisoned.
When Atticus gives Jem a gun, he tells him not to shoot at people. He also gives him another directive.
"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." (ch 10)
Scout tells Miss Maudie that Atticus rarely says it is a sin to do anything. She wants to know what makes mockingbirds so special.
"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." (ch 10)
Mockingbirds are gentle creatures. They also take on the characteristics of other, stronger or bolder birds. Boo Radley does the same thing. He is a shy man, and he hides most of the time. Yet he reaches out to the children by leaving them gifts.
Like mockingbirds, Boo is victimized by his society. People target mockingbirds because they make good targets. They are different. This is the reason people target Boo. Jem's description highlights what people see in him.
Boo was about six-and-a-half feet tall, judging from his tracks; he dined on raw squirrels and any cats he could catch, that's why his hands were
bloodstained- if you ate an animal raw, you could never wash the blood
off. (ch 1)
Anything different is a victim, even if the difference does not hurt anyone.
At the end of the book, the children finally get to meet Boo when he saves them from Bob Ewell. He has demonstrated that when you cultivate the mockingbird instead of shooting it, it is well worth the trouble.