In Harper Lee’s To Kill a Mockingbird, what characters represent a mockingbird?
In Chapter 10 Atticus gives Scout and Jem this advice:
Shoot all the bluejays you want, if you can hit 'em, but remember it's a sin to kill a mockingbird (90).
Miss Maudie explains this to Scout by telling her it is because mockingbirds are basically innocent creatures. They aren't nuisances, they don't eat gardens; they basically do nothing but sing.
So keep this in mind as you consider the symbolism of the mockingbird and apply to it to different characters. You could probably make arguments for several characters to be considered mockingbirds, but there are a few who are considered the most obvious choices.
The first is Boo Radley. The audience knows nothing about him except the rumors told by Miss Stephanie, which all make him out to be a monster, and the fantasies of Jem, Scout, and Dill, which further make him out to be a monster. But as the story progresses we see Boo leaving gifts for the kids in a tree, folding Jem's pants where he can find them, and finally saving Scout and Jem from the attack by Mr. Ewell. Boo Radley is made out to be an antagonist for much of the story when in reality he is a shy, innocent, and mostly good man.
The other most obvious mockingbird-character is Tom Robinson. It is pretty clear by the end of the trial that Tom Robinson is, in fact, innocent. But he is found guilty, and later killed in jail.
Atticus had used every tool available to free men to save Tom Robinson, but in the secret court of men's hearts Atticus had no case. Tom was a dead man the minute Mayella Ewell opened her mouth and screamed (241).