Birds have been uniquely designed for flight. Even species that do not fly--such as penguins and ostriches--have the same basic anatomical structures as other birds. There are some key characteristics of bird anatomy that will give us a better appreciation of their design:
Skeletal structure. 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 are an exception to this, since they have solid bones.
Respiratory system. Most of the air that enters a bird is not used for breathing; instead, it cools down the bird's internal tissues. In addition to lungs, birds have been provided with a system of air sacs. The air sacs make the bird lighter, so that it is buoyed up more easily by air or water. The sacs also make the respiratory system more efficient by providing increased surface area for it.
Four-chambered heart. Like people, birds have a four-chambered heart. This pumps enough blood through a bird's body to cope with the strenuous work of flight. The veins and arteries that supply blood to the wing muscles are especially large, since the body parts that are used in flight work the hardest.
Covering. Feathers provide a waterproof covering 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!
Feathers have their own unique anatomy. If you have a feather, you and your children 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.
Eyesight. Have you ever noticed how birds have to turn their heads to look at an object? That is because their eyes are almost immovable. 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 to fulfill the different eating functions required by each species of bird. 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?