How does the author use metaphor in the novel, Venco?

The yellow birds that fly around Meena and Wendy's house symbolize the freedom of existence. Wendy notes that yellow birds are often familiars for witches for somewhat unknown reasons. She compares the symbolism of the birds for witches to how Christians use crucifixes, telling Lucky "They are a physical reminder outside of our own bodies that we exist, that we are here" (162).