Fun with Science Club®


			Do birds use the stars as their guides during migration? Carrie Straight 05.14.01 Many small passerine (perching) birds migrate at night. Commonly these birds leave from 1 to 4 hours after sunset, but occasionally birds start their migration much later in the evenings. For many years scientists have asked the question: how do birds know when to migrate? Many hypothesize they can tell the direction by using the sun or stars, or both. To look into this question, some researchers in Sweden placed radio tags on some reed warblers, Acrocephalus scirpacaeus. Using an antenna and receiver, the researchers could follow the movements of the birds with the radio tags. The researchers made systematic observations and then recorded the movements of the birds and height of the sun and what stars were visible at the time of departure. If the scientists can understand what is visible when the birds first start to move, they might be able to find out how the birds know when is a good time to migrate. The scientists discovered that most of the reed warblers started their migration about 2 hours after sunset. No birds left before the first stars were visible, and many left when only stars remained to help determine direction of flight. When the reed warblers left during overcast skies, their direction of flight was more scattered which might mean that they need to see the stars to figure out the correct direction. A reed warbler knows when and which direction to migrate by looking to the stars!


			S. Åkesson, G. Walinder, L. Karlsson, and S. Ehnbom. 2001. Reed warbler orientation: initiation of nocturnal migratory flights in relation to visibility of celestial cues at dusk. Animal Behaviour 61: 181-189.