At the very end of Chapter 25, Mr. Underwood compares Tom's death to the killing of a mockingbird, specifically "to the senseless slaughter of songbirds by hunters and children." This tells us that he was killed for entertainment, not nutrition, and that he was killed out of habit (the hunters kill because that's what they do to birds) and by those who don't know any better (the children). The irony here is that the children in the novel do know better—it's the adults who don't, or who do know better, but don't act on it.
"Mockingbirds just make music.They don't eat up people's gardens;don't nest in corncribs;they don't do one thing but sing their hearts out."
This shows that Mockingbirds contribute to the society without expecting any recognition or reward.Tom Robinson was an honest and reliable worker,like what his previous employer,Mr Link Deas testified&he also helped Mayella without payment because he felt sorry for her.
This also shows that Mockingbirds do not harm anyone.Tom Robinson did not rape Mayella.He was honest,innocent and kind. He commended Mayella for treating the children to ice cream, he had the interest of the women and the children before he said "something not fittin'"and he also does not blame Mayella for causing him to be charged for rape.He was indirect to say that it was Mayella's fault,"I say she's mistaken in her mind",which shows his consideration and kindness because he does not want to ruin Mayella's reputation.He knows that Mayella had"broken a rigid code of our society"and she would be "hounded from our midst as unfit to live with".