Send a Songbird to the Neotropics |
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: