For the Birds: The Making of a Bird

Scarlet ibis has specialized bill, legs for wading,
and brilliant coloring
Stock photo

By Christine Southwick

What is the definition of a bird?

A bird is a warm-blooded egg-laying vertebrate with feathers, wings, a bill, and two legs.

All birds have feathers. There are just six basic feather types, whose complex combinations of types and colors can bedazzle even the most resistant-to-beauty humans. Swans have the most feathers; hummingbirds the least number.

All birds have wings — most can fly, some cannot; some can swim; some can both fly and swim.

Birds have two legs. Some are long and slender, others are short. 

Most birds have four toes, with three forward, and one to the rear which enables them to grasp branches. Raptors and owls have talons; some birds like Shrikes and Ravens wish that they had them. Woodpeckers, swifts and Osprey have specialized feet.

The beak of an eagle
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One of the most weight-reducing evolutions is the bill (beak) instead of teeth. Bills have specialized into different uses: skin-tearing, seed-crushing, water-filtering, mud-stabbing, and the most common, insect catching.

Most bills are straight and short — like bluebirds and most songbirds; long like Virginia Rails; long and curved like Ibis; or short and strong like eagles. The most extreme water filtering types are the bills of pelicans.

Another weight-reducing evolution, going back to dinosaurs, is hollow, strutted strong bones, including the heads. All birds have a “wishbone” (furcular) which protects the chest cavity, and helps propel the upward movement of wings, and a keel (sternum) where the strong wing muscles are attached.

Typical songbird foot
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Probably the most amazing adaptations are the heart and the lungs. These two organs allow birds to make those amazing long-distance migrations, often flying hundreds of miles without stopping.

Birds tend to have larger hearts than mammals (relative to body size). Bird hearts usually beat at lower rates than mammals of the same size but pump more blood per beat.

Birds’ lungs are unlike mammals, and are among the most efficient on this planet. Birds have smallish lungs, plus nine air sacs which rapidly distribute fresh oxygen throughout the body. Bird lungs do not expand or contract like the lungs of most mammals. The air flow is one directional, which allows then to fly rhythmically, and even sing while beating their wings. 

Bluebird has a straight and short beak
Stock photo

These adaptations of feathers, wing muscles, strong hearts and special breathing modifications allow birds to soar long and high, often higher than airliners.

Talk about taking one’s breath away….