Why do birds have feathers?

All birds have feathers and birds are the only animals that do!

• Feathers provide protection (from weather and injury).
• Feathers serve as insulation from cold and heat.
• Feathers help birds attract mates.

Feathers wear out and get old so birds must replace them every so often. Birds molt once or twice a year depending on the species. When bird molts the old feathers will fall out or are pushed out by the growth of new feathers.

 Birds will generally molt before they mate. The new feathers look bright and attractive and help males attract a female.

The starlings in these pictures show two very different plumages. The starling on the left is showing off its winter feathers while the bright shiny one on the right is ready to start breeding.

Did you know?
In late summer and fall, when a bird molts, it usually

photo by Lisa Barker

grows and replaces all its feathers gradually, but sometimes a bird loses all the feathers on its head at once. The result is a very strange looking bald bird! Don’t worry--usually the feathers grow back just fine.

Book recommendation:

What Makes a Bird a Bird? by May Garelick (Author) and Trish Hill (illustrator)

How do birds fly?

•  Birds have hollow bones that are very light and strong.
• Their feathers are light and the shape of their wings is perfect for catching the air.
• Their lungs are great at getting oxygen and very efficient  -- they can fly for very long distances without getting tired.
• They eat lots of high-energy food.

Kim Bostwick, a scientist at the Cornell Lab of Ornithology explains:

"Have you ever tried to move your open palm though the water really fast? Wide, flat

objects, like your hand, or  a paddle, are hard to move fast against water." It feels like the water is pushing back against you. Or have you put your hand outside the window while driving in a car and felt the air rush    against it? You can see-saw your hand up and down in the wind. In both cases you can feel the water or the air push against the flat palm of your hand. But if you turn your hand sideways, you can slip your hand through the water or air easily, right?"

"When a bird is flying, their wings are flat so that the air flows easily around it in the direction the animal flies (like your hand cutting through  the water or air). But something special and tricky happens here. As the air flows over the wing, the air flows faster over the top than the bottom because the wing is slightly curved on top. This means there will be  more air  on the bottom side (because the air is moving more slowly). When  there is more air on the bottom that leads to a push. And since the push happens against that wide flat part of the wing, this push lifts the animal. So a bird wing slices  in the air in the forward direction and gets pushed up from below; the net result is a flying bird!"
 

Why don't all birds fly?

 Some birds don’t fly. For example penguins, ostriches, emus, kiwis, and others.  It is thought that these birds lost their ability to fly because there weren’t any predators on the islands in which they lived.There are about forty species of flightless birds. There are none in North America. New Zealand has more species than any other country.