butterflies and ruby-throated hummingbirds have similar migrations even though one is a ____ and the other is a butterfly. Both species eat ____ . Both spend the _____ south of the United
States border and migrate _____
in the spring. Both species begin to arrive in the United States in
the month of _____, as they return to their _____ grounds in eastern North America. Both species move north as their _____
becomes ready to support their needs.
makes their migrations different? Do differences in _____ speeds matter?
Hummingbirds have been clocked flying 60 miles per _____ . They can fly across the _____ of Mexico in only 20 hours! Monarch butterflies only fly about _____ miles per hour unless the wind carries them faster.
Unlike monarchs, hummingbirds
have more than one source of _____. They can eat
insects and sometimes they even eat _____ that drips
from holes made in trees by woodpeckers. This means some hummingbirds
can migrate north before _____ bloom and still
find food. Monarchs must wait for flowers to _____ or they will not have food.
The _____ cycle of each species also affects the pace of its migration. Hummingbirds can complete the entire spring migration
in one _____. In contrast, the monarch's life cycle causes
a _____ . The monarchs that overwintered in
Mexico only live until mid-to-late April. They must lay _____ before they die. It takes
about one _____ for an egg to develop into an _____ butterfly. As adults, this generation completes
the migration throughout the northern breeding grounds.
Spring temperatures also affect both migrations in many ways. Because they are insects, monarchs are _____-blooded and are paralyzed
by cold _____ . Monarchs cannot _____ unless
their flight muscles are at least 55° F. Because they are birds, hummingbirds
are _____-blooded. They _____ fly in cold temperatures. However, they must _____ much more energy to keep their bodies warm.