Final answer:
Anne might conceive of birch trees as sociable due to their growth in clusters and the interaction of their leaves, which can resemble the dynamics of a social gathering.
Step-by-step explanation:
The query on why Anne thought birch trees were sociable does not seem to directly fit with the excerpts provided. However, birch trees, known for their distinctive bark and slender figures, are often found in clusters, with their branches lightly intermingling. These traits could be personified to suggest sociability, reflecting a sense of community or togetherness among them. A literary character might interpret their clustering and the rustling of their leaves as a form of communication, akin to mingling at a social gathering. Therefore, Anne might find birch trees sociable because they grow in groups, and their whispering leaves may resemble the comfortable chatter of friends.
In literature, such reflections on nature often help to illuminate a character's mindset or to draw parallels between the natural world and human society, which could be a reason Anne perceives birch trees as sociable.