What references to mockingbirds and songbirds can be found in Harper Lee's To Kill a Mockingbird? Why are the references significant?

Many references to songbirds can be found throughout Harper Lee's To Kill a Mockingbird.

In Chapter 10, Lee establishes the symbolism of mockingbirds and songbirds in general when she has Miss Maudie explain to Scout that her father is correct in thinking "it is a sin to kill a mockingbird" because they are innocent creatures that do nothing but bring pleasure by singing, unlike other breeds of birds that are nuisances. Later, Lee draws parallels between the innocent mockingbird and characters to portray those characters' innocence.

One parallel between the innocent mockingbird and Tom Robinson is drawn in Chapter 25. Soon after his death, Scout reports reading an editorial written by Mr. B. B. Underwood, editor and owner of The Maycomb Tribune. In the editorial, Mr. Underwood raves about the injustice of shooting Robinson. Scout paraphrases his ravings in the following:

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 (Ch. 25).

In other words, in Mr. Underwood's view, since Robinson was crippled, he was obviously innocent of the crimes he was being charged with and, therefore, it was a sin to kill him, just as it is a sin to kill innocent songbirds such as mockingbirds. Even in Chapter 25, we see Lee continue to use her symbolism of mockingbirds to signal innocence in people.

One reference to songbirds that is a bit different from others in the book can be found in Chapter 28. On the Halloween night the children are attacked, they hear a mockingbird as they walk past one of the oak trees in front of the Radley Place. Scout describes the bird's singing as such:

High above us in the darkness a solitary mocker poured out his repertoire in blissful unawareness of whose tree he sat in, plunging from the shrill kee, kee of the sunflower bird to the irascible qua-ack of the bluejay, to the sad lament of Poor Will, Poor Will, Poor Will (Ch. 28).

The last songbird's call is the most interesting symbolically. The call "poor will, poor will" is the call of the North American bird named the whip-poor-will, also spelled whippoorwill. Native Americans tribes have often associated whip-poor-wills with omens of death. As a result, whip-poor-wills have become known to "symbolize natural disasters, imminent trouble and aching solitude," as well as imminent death (The Nature Conservancy). Hence, the mockingbird in Arthur Radley's tree is meaningful on multiple levels. First, as a songbird, it symbolizes Arthur's innocence. Second, in mimicking the whip-poor-will, the mockingbird symbolizes Arthur's "aching solitude," allowing the reader to deeply empathize with Arthur. Third, in mimicking the whip-poor-will, the mockingbird foreshadows the imminent peril the children are in due to Bob Ewell's desire for revenge.

Yet, since it is a mockingbird imitating a whip-poor-will and not just a whip-poor-will singing, we know the mockingbird has deeper symbolic meaning than just foreshadowing impending doom. Interestingly, the mockingbird is also imitating the song of the bluejay, and bluejays symbolize, among other things, faithfulness, intelligence, determination, and assertiveness. Hence, in imitating both the whip-poor-will and the bluejay, the mockingbird not only foreshadows impending doom but also symbolizes and foreshadows Arthur Radley's upcoming moment of bravery; it symbolizes his faithfulness to the children, his intelligence in figuring out how to rescue them, his determination to rescue them, and his assertiveness in his rescue mission, despite any consequences his rescue may bring him.