According to Miss Maudie's definition in chapter 10, mockingbirds represent any innocent, defenseless being who needs on protection from harmful, selfish people. Tom Robinson and Boo Radley are the two most memorable mockingbirds, and there are several notable quotes that depict Boo Radley as a symbolic mockingbird. The most important quote portraying Boo Radley as a mockingbird can be found at the end of chapter 30, when Scout listens to Sheriff Tate's reasoning for why he refuses to thrust Boo into the community's limelight.
Atticus asks Scout if she understands Sheriff Tate's explanation, and she replies, "Well, it’d be sort of like shootin’ a mockingbird, wouldn’t it?" Scout's quote directly compares Boo Radley to a mockingbird because he is defenseless and relies on protection from others. Boo demonstrates his compassionate nature by rescuing Jem and Scout from Bob Ewell but remains a sensitive, vulnerable person. Sheriff Tate knows that Boo Radley would not benefit from increased popularity and decides to not mention his role in saving Jem and Scout.
Another quote about Boo Radley being a mockingbird can be found in chapter 26 when Scout sympathizes with him. Scout thinks about Boo Radley and says,
Mr. Nathan Radley could still be seen on a clear day, walking to and from town; we knew Boo was there, for the same old reason—nobody’d seen him carried out yet. I sometimes felt a twinge of remorse, when passing by the old place, at ever having taken part in what must have been sheer torment to Arthur Radley—what reasonable recluse wants children peeping through his shutters, delivering greetings on the end of a fishing-pole, wandering in his collards at night? And yet I remembered. Two Indian-head pennies, chewing gum, soap dolls, a rusty medal, a broken watch and chain. Jem must have put them away somewhere.
Scout's quote depicts Boo Radley as a mockingbird because he is portrayed as a harmless, caring neighbor, who generously gives them gifts without wanting anything in return. He is also vulnerable and cannot prevent the local children from tormenting him. Similar to mockingbirds, Boo Radley relies on the kindness of strangers and causes no one harm.