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How Birds Fly:
An In-Depth Journey North Lesson

Answers to Flight Lesson Questions

Question 1: If gravity pulls everything down, why do helium balloons go up?

Gravity DOES pull on helium balloons. But air is denser (heavier) than helium, so gravity pulls air harder than it pulls helium; the air sinks below the helium. The helium floats higher and higher above the heavy air until it gets high enough that the thinning atmosphere has the same density. That's when the helium balloon stops rising.

Question 2: Why might bird wings be more adaptable to flight than bat wings?

Let's say a large falcon grabs for a flying bat with its talons and misses, except one sharp talon slices into the wing. The bat wing, made of thin skin, needs stitches to hold the skin together until it heals, but that isn't possible in nature. So even if the bat narrowly escapes the falcon, if its wing is torn it can never fly again and will eventually die. If the exact same thing happens to a bird, the talon will merely slice into feathers, usually just separating them and messing them up a bit, but the bird can fix that with preening. Even if some of the feathers are torn out, the bird will quickly grow new ones.

Also, wings do hard work. Skin OR feathers eventually wear out. That's why birds grow new feathers once, twice, or sometimes three times a year. Bats, in contrast, can't grow new wings when the old ones get old and worn.

Question 3: Why do herons and cranes fly differently?

Herons eat fish, which have fairly dense bodies with tough outer skin and scales. They kill these fish by striking them HARD with their strong, sharp, dense beaks. Their neck muscles must be strong, and relatively heavy, too. So in flight they pull their heavy neck and beak in, closer to their center of gravity. Cranes eat some frogs, snakes, and other animals, but pick at them rather than striking. For these reasons, neither a crane's beak nor its neck needs to be as dense. This means cranes have little extra weight in front of their center of gravity and can fly the simple way with their neck stretched out, like geese and swans.

Question 4: Can you think of some kinds of birds that don't tuck their legs in as they fly?

Some examples of birds that don't normally tuck in their legs are cranes, herons, loons, and long-legged shorebirds. Bird expert Laura Erickson once watched cranes staging along the Platte River in Nebraska during a frozen spell in March when temperatures were well below zero. Under these extreme conditions, the cranes were tucking in their legs! This was certainly more to keep their feet warm than to make them aerodynamic.


Journey North is pleased to feature this educational adventure made possible by the

Whooping Crane Eastern Partnership (WCEP).

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