To Fly

Have you ever wondered how birds fly? This is a subject that has fascinated mankind for ages. In many ancient cultures they viewed a birds ability to fly as something magical or associated it with the supernatural. The truth is that through many many centuries birds have evolved several adaptations which have assist in their ability to fly.
In order to fly birds need to be light weight. Instead of having heavy bones and teeth like we do most birds have hollow bones and a light weight beak. They also have a much more efficient cardiovascular system then we do. Their lungs process oxygen more quickly efficiently and their heart beats much faster. This is necessary because it takes a lot of energy to fly.
Perhaps the coolest adaptation for flight though are their feathers. Birds have between 1,000 to 25,000 feather. Feathers are made of a substance called keratin. Even though they are strong and durable they are also very light. The spine of the feather is called a shaft. The shaft runs the length of the feather and it is hollow inside. Connected to the shaft are branches called barbs. The barbs connect to each other giving the feather a solid appearance however there is space between them which helps to keep the feather light. Each bird has several different type of feathers each serving a different purpose. It is important for the bird to keep their feathers in good shape so they spend a significant part of each day preening. Once or twice a year, depending on the type of bird, they will lose their feathers and new replacements will grow in. This is called molting. Most birds only molt a couple of feathers at a time so that they can continue to fly while their feathers are being replaced. However some waterfowl molt all their feathers at once leaving them flightless for a week or two.