Migratory Orientation in the Indigo Bunting, Passerina Cyanea
Part I: Evidence for Use of Celestial Cues

Emlen, S.T. (1967). The AUK, 84:309-342.

The Zugunruhe orientation of caged Indigo Buntings was tested both outdoors under the natural night sky and inside the Robert T. Longway Planetarium in the fall of 1964 and the spring and fall of 1965. During these three seasons, data were obtained from 23 different birds for a total of 33 "bird seasons." In 24 of these cases (73 percent), the birds displayed a consistent tendency to orient in the direction appropriate for the migration season in question; random results were obtained in an additional 8 cases (24 percent).

The individuals demonstrating directional preferences under the night sky continued to orient correctly under artificial planetarium skies set for local conditions, reversed this direction when the north-south axis of the planetarium sky was reversed 180 degrees, and lost all ability to orient when the starts were turned off and the dome diffusely illuminated.

These results support the hypothesis that Indigo Buntings are able to obtain directional information from the starry sky.