| Time to Go!
Spring migration begins every March in a flurry. The monarchs are in a race against _________. They can't stay in _________ any longer, but they can't move north too quickly either. The _________ of the monarchs' spring migration must be precise. How do they know when to leave, and why do they go now?
____________ is Falling
Time is running out because the _________ the monarchs stored for the _________ is almost gone.
____________ are Rising
Time is running out because air _________ are rising at the monarch colonies. As it gets warmer and warmer, the butterflies burn their remaining _________ faster and faster.
____________ is Scarce
Time is running out because the monarch's winter habitat is as dry as a bone by March. Mexico's dry season began when the monarchs arrived in November. Now the colonies are breaking up as the butterflies fly out in search of _________.
Monarchs are ____________
Time is running out because _________ begins as temperatures rise. Monarchs live for only a few weeks after they _________.
Monarchs Need ____________
Time is running out because monarchs must lay their eggs on _________. _________ is the only food their young caterpillars can eat. Imagine how much _________millions of monarchs will need!
____________ is Coming!
Meanwhile, habitat is _________ across North America. Milkweed and flowers will soon grow in the north. The area in red shows where the monarchs will migrate. Look at how much space the monarchs can have!
Sensing Change
"The spring _________ is probably the trigger for monarchs to migrate," says Dr. Lincoln Brower. Day and night are 12 hours long on the spring _________. The monarchs may use day length as a cue to migrate.
Here Come the Monarchs!
With only a few weeks to live, the monarchs are racing northward. They are carrying the seeds of the next generation. Will the monarch's breeding _________ be ready when the butterflies arrive?
Track Spring's Journey North
Watch how your backyard _________ changes with the spring season. Monarchs will appear like magic when their _________ is ready. Please report your "first sightings" of the season to Journey North.
|