with Neotropical Migratory Birds
Their Way--The Stars as a Compass
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.
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 drawing below (Step D), 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 each 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.
After students make their drawings, help them visualize the full rotation
of the stars by making Sky Map Star Clocks with the reproducible patterns
and instructions we've provided.
It seems there are 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: