Monarch 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.

What 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.