GENERAL ADAPTATIONS BIRDS HAVE EVOLVED FOR FLIGHT
Birds belongs to a class called aves. They are the only group of animals to posess feathers and they are best known for their ability to fly. These warm blooded vertebrates have feathers covering their skin and their forelimbs. The taxanomic point of view shows that there are about 8.800-10.200 living bird species and their size range from the tiny hummingbirds to the huge ostrich.
Fossilisation shows that dinosaur and reptile are the only great ancestors of the birds. According to the skeletal bones it was found that bone the close ancestor of the birds were arboreal or evolve flight from the trees nor they were physiologically intermediate between typical reptiles and living birds, nor that their feathers evolved for flight. The ancestors of birds were terrestrial,fast growing and active animals.
Feathers are made of a protein called keratin. They are made of thousands of branches called barbs. Feathers grow in specific areas called feather tracks. Between the feathers tracks there are down feathers which are used to keep the body weight. The spine down the middle, called the shaft, is hollow. The vanes are on the two halves of the feather. They are made of thousands of branches called barbs. Because there are many spaces between these barbs, a feather has as much air as matter. They grow from a bump of skin. Growth starts by a tip of a feather. After the bird hatches then the tip separates and looks like fuzz on the baby bird. Pin feathers are rolled inside the sheath. For a bird to survive it depends on the condition of its further. They take a lot of time caring for their feathers and this is called preening. Their feet and beaks are used to arrange and to clean their feathers. They chew each feather from the base to the tip meaning that they bath a lot. Feathers protect the skin of the bird, during winter they can be fluffed up and in summer they can be squeezed down. They also help in making the nest.
Different birds have different types of feathers but all birds have feather on their wings. The wing on a bird serves as the basic structure for flight. The shape of the wing allows the bird to fly. During the flight the tail of the bird also plays an important role, it acts as the rudder balancing and steering the bird. If the tail is turned downward it acts like a brake, helping the bird to stop. Everything about the bird is made perfectly for flying. The entire body inside and outside is designed for flight. Every part must give maximum power with a minimum of weight. The heavier the bird the bigger its wings need to be and the bigger the wings, the more muscles are needed to move them.
The easiest way to fly is to be light. Birds have feathers that are very light in weight. The bones that birds have are made for lightness. Birds have fewer bones than most animals. The bones they have are hard but thin. The biggest bones in flying birds are the breast bone and the shoulder bones. The shape of the wing is called the airfoil. When the wing moves the air goes above and below. The air moving over the upper surface has to be faster than the air on the lower part of the wing. The shape of a wing is called an airfoil. As the airfoil moves through the air, air goes above and below. The air flow over the upper surface has to move farther than the lower part of the wing. In order for the air flows to make it to the edge of the wing at the same time, the top air must go faster.
1. Wikipedia contributors, the free encyclopedia [Internet] [Cited 2006 May 12] Available From: http://www.fi.edu/wright/again/wings.avkids.com/wings.avkids.com/Book/Anials/intermediate/birds-01.html
2. Wikipedia contributors, the free encyclopedia [Internet] [Cited 2006 May 12] Available From: http://animals.about.com/z/js/o.htm?k=birds&d=Birds&r=http%3A//animals.about.com/od/birdsastudyguide/a/introtobirds.htm
3. Wikipedia contributors, the free encyclopaedia [Internet] [Cited 2006 May 12]
P.O Box 395
Tel: +27 12 841 2133
Cell: +27 73 121 3589