Indigo Buntings do not rely on individual stars or the general brightness of groups of stars, but instead use them as clues in navigation. Prior experiments removing certain constellations and stars (Big Dipper, Cassiopeia or Polaris) from the sky had minimal effect on Zugunruhe. Indigo Buntings do use the northern sky to help navigate both in the fall and in the spring. It was thought that the bunting has an internal clock, being able to compensate for the movement of stars. However, temporal compensation for stellar motion is not a part of their migratory methods.