Thank you for contacting Cooperative Extension. For building a rabbit hutch, avoid using treated wood as it contains arsenic but hardwoods should be fine. Regular untreated pine can work as well.
As quoted from a fellow rabbit hutch builder, "Most untreated woods are fine but not redwoods which are toxic. Cedar and pine in chips or shaving forms are said to be hazardous because they more readily release the aromatic oils in this form. As a solid plank of wood, it's fine to use. [B]irch and aspen are bunny safe so they would be good options also."