Send a Songbird to the Neotropics

Lesson #6: Finding Their Way--The Stars as a Compass

Background
Imagine this: A young bird lies awake at night in its nest looking at the sky and observing something few people realize: The night sky rotates in a complete circle every 24 hours. All the stars appear to move around the sky in a big circle except one-the North Star. This is because the North Star is positioned very near the North Pole, the axis of the Earth's rotation. Therefore, the North Star seems to stay in the same place all night. Explorers have used the North Star for navigational purposes for centuries. It might be a surprise to know that animals can use stars as a compass too.

Activity
A. Ask students how they might use the North Star as a compass. Show them how to locate the North Star in the night sky. To do this they must be able to find the Big Dipper. As shown in this diagram, two stars in the bowl of the Big Dipper point to the North Star.

B. Have students make two sketches of the night sky. The sketches must be drawn on the same night, preferably one at dusk and the other at dawn. (If this is not possible, make certain that the sketches are drawn at least four hours apart.) Each sketch must include the position of the Big Dipper and the North Star. Students should draw as if they are lying on their backs and looking up at the sky. Each sketch should indicate the directions north, east, south, and west. Students should also note the time the drawing was made.

C. The next day, help students visualize the full rotation of the stars by making paper models. Each student should draw a 24-hour clock on a circle. On a smaller disk, have them draw the North Star and Big Dipper. A paper fastener can be used to connect them. By rotating the model, students can compare the timings of their drawings to the position of the stars.

D. (Optional) Enclose your star compass in your fledgling's survival kit. But watch its weight! Remember: Your full bird and survival kit can weigh no more than 140 grams (5 oz.) or it can't migrate! See Lesson, # 8: Creating Your Baby Bird and its Survival Kit

Extension
There seems to be at least three primary cues from which animals could develop their sense of direction. These cues come from the stars, the sun, and the Earth's magnetic field. Research suggests that different animals navigate using several of these cues in combination, rather than relying on a single method. For more information: