Sun-Arc Hypothesis

The first experiment, done in the 1950s by the German, Gustav Kramer,  suggested that birds use the sun for directional positioning. The birds were housed in a circular cage that allowed them to see the sun. During migrating season,  they would face Northeast at all times, as if they were preparing for migration. However, on cloudy days they would not have any inclination towards any direction. Similar results were also observed in pigeons that were exposed to varied climates and asked to return to their homes. The birds in clear weather excelled where as the subjects in poorer conditions were unsuccessful or less efficient.  Of note, these birds were observed correcting for the sun’s position,  a technique that was noted to be similar to telling time.  This phenenomenon, dubbed the sun-arc hypothesis, was supported by an experiment where a lightbulb was substituted for the sun and the birds naturally corrected in anticipation of this pseudo-sun setting.