What does hearing a bird outside the hospital reminding sal of home in walk two moons?

Hearing a bird outside the hospital reminds Sal of home because it represents a connection to nature and the outside world. Throughout the novel, Sal finds solace and comfort in nature, and the bird's song reminds her of the familiar and comforting sounds of home. She feels a sense of nostalgia and longing for her home and family, and the bird's presence provides a sense of connection to the outside world, beyond the hospital walls. The bird's song also symbolizes freedom, as it can fly and move freely, in contrast to Sal's confinement in the hospital.