Birds have special ways of surviving. Their bodies are a major one. Special lightweight bones help them fly and feathers help protect them from bad weather.
Bones. Birds have very lightweight bones. Their bones are also very strong, so that they do not break under the pressures of flight. The bones in bird legs and wings are hollow, providing space for tiny air sacs. Flightless birds, however, have solid bones.
Lungs. Most of the air that enters a bird is not used for breathing! It is used to cool down the bird's insides, which can easily become heated during flight. Birds have lungs and also a system of air sacs. The air sacs make the bird lighter, helping it float in air or water.
Heart. Like people, birds have a four-chambered heart. It pumps blood very quickly through a bird's body to cope with the hard work of flying. The veins and arteries that supply blood to the wing muscles are especially large, since the body parts that are used for flying work the hardest.
Feathers. Instead of skin or fur, birds are covered with feathers. Feathers provide a waterproof layer for birds and act as an insulator so they can maintain a high body temperature. Birds usually need to maintain a body temperature of 110 degrees Fahrenheit! Do you know what temperature our bodies maintain? (Answer: 98.6 degrees Fahrenheit.)
Feathers have their own unique anatomy. If you have a feather, you might want to observe the different parts. Use a magnifying glass to see the tiniest parts. The hard, stem-like section of the feather is called the rachis. The "branches" of the feather are called vanes. Each vane is made up of more tiny parts. The stem of the vane is called a barb. Branching from the barb are tiny barbules, each with little hooks on them. The hooks work like Velcro, to connect the vanes of the feather and hold them together. This is why it is so difficult to separate the vanes of a feather from each other. Learn more about feathers here.
Eyes. Have you ever noticed how birds have to turn their heads to look at an object? That is because their eyes aren't able to move very much. However, birds are able to see a greater range of the color spectrum than people can. They also have the ability to focus on two different objects out of each eye! Each eye has two foveae, the part of the retina which "sees" most clearly.
Bills. Bills are uniquely tailored for the different eating functions required by each species of bird. They don't have teeth, so their beaks are important! Birds with short beaks, such as sparrows and finches, eat small seeds. Cardinals and grosbeaks have slightly larger, stubby bills to hold the large seeds that they eat. Meat-eating birds, like hawks and eagles, have hooked bills to tear their prey. Woodpeckers have long, narrow bills for extracting insects from dead wood. Toucans have large, hollow bills for collecting fruit and cracking it apart. Most sea birds have long bills, to capture and hold fish.
Your children might enjoy guessing what different birds eat. Collect pictures of different kinds of birds from nature magazines or books. Hypothesize with your children about what kind of food each bird eats, based on its bill shape and size. To check your hypotheses, use a bird guide or an encyclopedia and read about what each bird eats. Discuss how close your guesses were to the answers. Do you have a general idea now of how bill shape and size fit each bird?
Most birds use flying as their primary mode of transportation. However, some birds can't fly at all! (You'll learn more about them below.) A bird's lightweight bones and specially designed wings make flying easy. They also have special strong muscles to support their wings during flight and to keep them moving, even when they have to fly over very long distances. A bird's wing is curved from the front to the back, the same way an airplane's wings are. The special shape allows the air to push the bird along as it flaps its wings. There is more pressure from the air pushing up (from the bottom) on the wing than there is pushing down (from the top of the wing). This is called lift. It helps a bird take-off and stay in the air.
Besides flapping, there are other techniques birds use to fly. They can stretch out their wings and glide slowly down towards the ground without flapping. Ducks often glide down to land in water.
A similar way of flying is called soaring. Instead of going downwards, though, a bird can soar when it stretches out its wings over warm air. Since warm air rises, it pushes the bird upwards. Hawks and eagles often soar.
Some birds can fly sort of the way helicopters do — by hovering! In order to hover, a bird must flap its wings very very quickly; hummingbirds flap their wings over 50 times per second! This quick movement allows them to fly backwards as well as forwards. They can also fly up or down, and side to side, much like a helicopter.
All birds have wings, but not all birds can fly! Some birds can't fly at all and are called flightless birds. Their wings aren't designed for flying. Penguins, for example, use their short wings like flippers to help them swim. In fact, penguins are excellent swimmers — it's not unusual for one to swim a total of over 100 miles just to find food. Flightless birds usually have much smaller and shorter wings than birds that fly. Their feathers are also smaller and are symmetrically shaped (each half of the feather looks the same - like a butterfly's wings). Birds that fly have asymmetrical feathers (one side of the feather is usually larger and more rounded). Birds that don't fly also usually have more feathers covering all of their bodies. Kiwi birds, Emu, Ostriches, and Penguins are a few kinds of flightless birds. Some flightless birds are now extinct, such as the Dodo bird.