Every September, monarch butterflies migrate to Mexico by the millions. They stay there for the winter. They live in the branches of fir trees. Tall trees keep the butterflies safe from the rain. Trees also help to block the dangerous cold night air. Scientists are worried about monarch butterflies. The winter of 2010 was very troubling. There were fewer butterflies in Mexico that winter. In fact, it was the smallest population since 1993. Scientists think that they know why. Many fir trees are being cut down in Mexico. Without enough trees, the butterflies cannot survive.

Do It!

The butterflies use the trees for _________.

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A directions
B closets
C shelter
D food