Final answer:
The question seems to be about 'To Kill a Mockingbird' but actually references various other literary works. There is no 'fourth person under the tree' in Harper Lee's novel, and the provided passages instead cover a range of scenes featuring nature, animals, and suspense.
Step-by-step explanation:
The query regarding the fourth person under the tree appears to be a confusion with a passage from To Kill a Mockingbird. The reference provided does not align with the classic novel by Harper Lee but seems to mix elements from different literary works. No such event involving a fourth person under a tree making strange sounds occurs in To Kill a Mockingbird. In fact, the excerpts shared span various texts, encompassing encounters with natural elements, a variety of animal interactions, and experiences of fear or suspense within a natural setting. Each piece provides an atmosphere of tension or highlights the character's emotion in response to their environment or situation, which is a common technique in literature to build mood and advance the narrative.