Birds are some of the most amazing animals on earth. Most have the
ability to fly. Some use ground travel. Some use claws, others use only their
beaks. Birds come in many varieties of colors and sizes.
Birds are warm-blooded, egg-laying creatures from the aves class. Along
with the obvious feathers and wings, birds have other adaptations for flying
such as a wide keel on the sternum, with large wing muscles attached, air spaces
and sacs throughout the body and bones, to decrease their weight, and they have
various bone fusions and reductions to strengthen and streamline their body.
There are more than 8700 species of birds. Their habitats range from icy
shores of Antarctica to the hottest parts of the tropics and from mountains,
deserts, plains, and facts to open oceans and deeply urbanized areas.
The sizes of birds range from the tiny bee hummingbird, which has a
total length of two and a half inches, to the albatross, which has a wing span
of eleven and a half feet. The largest bird is a bird that cannot fly, the
ostrich. Ostriches can stand almost eight feet high and can weigh near 350
pounds. Other extinct birds have been measured to stand over ten feet high.
The evolution of birds is still being argued. Most people believe that
birds evolved from reptiles. Because of birds mainly delicate bones, few fossils
have been left behind for scientists to study. The earliest bird fossils come
from archaeopteryx. The fossils that have been discovered from archaeopteryx
include six partial skeletons and one single feather. Archaeopteryx , unlike
modern birds, had teeth, a reptile like tail, and three claws on each wings.
Scientists think it could fly, but only weakly.
Approximately 85 species and 50 sub species have become extinct in the
last 300 years. Over half of them occurred in the 1800’s. Another thirty percent
occurred in the 1900’s. Over ninety percent of these extinction’s were island
forms, which are particularly vulnerable to human interference. Destruction of
habitat is the biggest cause of extinction. Other causes are the introduction of
predacious animals, and disease plays it’s part too....