Food for thought. Man has found fossilized bones of prehistoric creatures we call Pterodactyls. Their wings were similar to the style of bats, but in
the form of a large reptile. These creatures had wing spans of at least 20 feet. If these creatures were alive today they would not be able to get off
the ground. If it jumped off a cliff to get a start it would break its wings because of it's weight.
Condors of California and South America are the largest capable of flying. They measure around 4 1/2 feet long and have a wingspread of around 11
feet.
To achieve and maintain flight, a bird has to have tremendous muscles. Over 30 percent of a hummingbird's weight is in its flight muscles. In fact,
the flapping motion is one of the most strenuous activities in the entire animal kingdom. The heavier the bird, the more difficult is flight. The top
weight range of flying birds is about 20 - 30 pounds. Examples that come to mind of this upper limit are mute swans, California condors, and some
pelicans.
birding.about.com...
Flightless birds:
www.enchantedlearning.com...
www.madsci.org...
How many birds do you know that cannot fly?
Could it have been easier to fly in the ancient world? If so, what made it possible?