Birds can fly because they have low weight and lots of power. Their feathers, wings, hollow bones, warm bloodedness, powerful breast muscles, and a strong heart all contribute to this ability. Last week, we discussed body weight and feathers. This week we cover:

Strong Body Systems
The avian repertory system includes a unique system of five or more pairs of air sacs connected with the lungs. The air sacs provide a one-way traffic of air, bringing in a constant stream of unmixed fresh air. This is in contrast to mammals, where stale air is mixed more inefficiently with fresh. Birds also have a four-chambered heart, which allows double circulation. That is, the blood makes a side trip through the lungs for purification before it is circulated through the body again. Bird hearts beat rapidly, and relative to overall body size, they are large and powerful.

Golden Eagle in flight
Golden Eagle in flight

Even in the foods they select to feed their “engines”, birds conserve weight. Their foods – seeds, fruit, worms, insects, frogs, rodents, fish, and so on – are rich in caloric energy. They usually do not eat foods such as leaves and grass for this reason. Furthermore, the foods most birds eat are burned quickly and efficiently. Fruit fed to a young Cedar Waxwing will pass through its digestive tract in less than 30 minutes. Birds also utilize a greater proportion of the foods they eat than do mammals.

In all these characteristics, we see that birds are incredibly well-suited for flight and it is no wonder we admire them for this ability. Amazing!

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