how are birds adapted for flight

Flight Adaptations: In addition to wings and feathers, birds have developed a variety of physical characteristics as a result of their ability to fly. For heavier-than-air flying machines—birds included—having a structure that blends strength and light weight is essential. In birds, this is sometimes achieved by the “pneumatization” (hollowing) of the remaining bones and the fusion and removal of some others. While most vertebrates have separate finger and leg bones, some vertebrae, as well as some bones of the pelvic girdle, are fused into a single structure in birds. And many tail, finger, and leg bones are missing altogether. Unlike human bones, the bones of birds have many hollows that are linked to the respiratory system. The internal strut-like reinforcements in a bird’s major wing bones prevent the cylindrical walls from buckling. Because bird bones were pneumatized, it was thought that birds’ skeletons weighed proportionately less than those of mammals. Careful studies by H. D. Prange and his associates have demonstrated that this is untrue. A bird’s skeleton is subjected to greater demands than that of a terrestrial mammal. Either all of the bird’s forelimbs or all of its hindlimbs must be able to sustain it. It also needs a sternum, or deep, sturdy breastbone, to which the wing muscles can be attached. As a result, although certain bones, particularly the leg bones, are heavier than those found in mammals, other bones are substantially lighter. The avian skeleton is an example of parsimony thanks to evolution; it lightens where it can and adds weight and strength when needed. The results can be quite amazing: not all birds have the same degree of skeletal pneumatization. For example, a seven-foot-span frigatebird’s skeleton weighs less than the feathers covering it. Certain diving birds, like loons and auklets, have relatively solid bones to reduce their buoyancy and facilitate diving. Compared to birds with lighter skeletons, those birds typically have less flying skill. Aside from hollowing out their bones, birds have discovered other methods to reduce the weight. For example, they only significantly enlarge their reproductive organs (testes, ovaries, and oviducts) during the breeding season. They maintain these organs small for the majority of the year. Birds’ respiratory systems are also modified to meet the needs of flight. Given that flying is a more taxing activity than walking or running, it makes sense that a bird’s respiratory system would be proportionately larger and far more efficient than ours. An average mammal only dedicates around one-twentieth of its body volume to its respiratory system, compared to approximately one-fifth in the case of birds. The respiratory systems of mammals are made up of tubes that join the lungs, which are blind sacs, to the mouth and nose. Because the lungs do not completely collapse with each exhalation, only a portion of the air within them is exchanged during each breath, leaving some “dead air” behind. The lungs of birds, on the other hand, are smaller and less flexible, but they are connected to a system of large, thin-walled air sacs in the body’s anterior and posterior regions. These are then linked to the air spaces within the bones. The clever system that allows air to enter and exit the bird’s lungs in two stages is a result of evolution. An inhaled breath enters the posterior air sacs before exiting the body and entering the lungs. The air from the first breath travels from the contracting lungs into the anterior air sacs when a second breath is inhaled into the posterior sacs. The air from the first breath exits the bird through the anterior air sacs during the second exhalation, whereas the air from the second breath enters the lungs. The air thus moves in one direction through the lungs. Every bird has this one-way flow system, and the majority also have a second, two-way flow system that can account for up to 20% of the lung volume. Air is directed down tiny tubules in both systems, which interdigitate with capillaries that carry venous blood low in oxygen. The oxygen-rich air at the tubules’ beginning is in close contact with the oxygen-starved blood; further down the tubules, the oxygen contents of the two media are equal. The lungs of birds are anatomically very complex—their structure and function are barely described here—but they produce a “crosscurrent circulation” of blood and air that allows for a higher capacity than that of mammalian lungs for the exchange of oxygen and carbon dioxide across the thin intervening membranes. The beats of a bird’s wings have nothing to do with the rhythm of its two-cycle respiratory pump, despite popular belief. Flight movements and respiratory movements are independent. The pumping action of the heart is what delivers oxygenated blood to the tissues and removes deoxygenated blood (which is packed with carbon dioxide) from them. The ratio of breaths to heartbeats in birds can be relatively low due to the efficiency of their breathing apparatus. Regardless of size, a mammal takes one breath every 4.5 heartbeats, while a bird takes one breath every 6–10 heartbeats (depending on the size of the bird). A bird’s heart is strong, large, and has a basic structure similar to that of a mammal. It is a four-chambered device with two side-by-side pumps. Blood rich in oxygen is drawn from the lungs by a single, two-chambered pump and sent to the tissues in anticipation. The blood with low oxygen content is taken from the tissues by the other pump and pumped into the lungs. The separation of the two types of blood, which is not entirely present in fish, amphibians, or reptiles, gives birds’ circulatory and respiratory systems the capacity to withstand the demanding conditions of flight. Most birds’ flight muscles are red in color (“dark meat”) due to the abundance of fibers that contain red oxygen-carrying substances like cytochrome and myoglobin. They are made for prolonged flight and have an abundant blood supply. Gallinaceous birds such as pheasants, grouse, quail, and others have lighter-colored muscles, also referred to as “white meat,” which contains fewer of these fibers. They appear to be able to handle a heavy workload for a brief period of time and have a good blood supply, but they tire more quickly. A quail will run out of energy and be unable to fly if it flushes multiple times in a row. Eventually, of course, being able to maintain flight or fly quickly is useless if you are constantly colliding with objects. Despite their prowess at simplifying, reducing in size, or doing away with completely superfluous parts (such as bladders), birds have not skimped on nervous systems. The brains of birds are comparatively larger than those of lizards and even on par with those of rodents. The brain has many processing areas to organize the information it receives from the sharp eyes and is linked to them. The nerves in a bird can quickly transfer brain commands to the muscles that control its wings. The Golden-crowned Sparrow is able to swiftly maneuver through the branches of a thicket and avoid being caught by a Sharp-shinned Hawk because of its keen vision, fast reflexes, and rapid nerve transmission via short nerves. SEE: Metabolism and Temperature Regulation; Hawk-Eyed Copyright ® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye.

In addition to developing wings, birds also acquired numerous other adaptations that enable flight. Feathers offer waterproofing, insulation, and a lightweight way to take to the air. Birds have honeycombed or hollow bones, reducing body weight. And birds evolved a light, useful keratin beak in place of heavy jawbones and teeth. The majority of birds eat high-calorie, high-energy foods like meat, seeds, and fruits, which add as little weight as possible to their payload. Additionally, their food is processed quickly, preventing waste from weighing them down.

### Bird sounds provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. 40786 recorded by G. F. Budney, 107629 recorded by Todd A. Sanders, 63085 recorded by David S. Herr, 21090 that Bruce Rideout captured, and 3754 that Arthur A Allen and David G. Allen. Nancy Rumbel and John Kessler composed and performed the theme music for BirdNote. © 2017 Tune In to Nature Producer: John Kessler Managing Producer: Jason Saul Associate Producer: Ellen Blackstone org July/August 2017/2019 / March 2023 Narrator: Michael Stein ID# flight-12-2017-07-05 flight-12.

First of all, feathers. Feathers are incredibly lightweight and offer insulating, waterproofing, and flight capabilities.

Birds have very light, honeycombed or hollow bones. Additionally, birds have evolved a very light and useful beak in place of a bulky mouth full of teeth and jawbones.

What birds eat also helps them stay light for flight. The majority eat foods high in calories and high in energy, such as meat, fruits, and seeds. These are foods that provide a lot of value for the money while contributing as little as possible to a bird’s payload. Additionally, birds’ food is quickly digested, preventing waste from weighing them down.

FAQ

How do birds adapt to their flying lifestyles?

Many of the bones in a bird’s body are hollow, making the bird lightweight and better adapted to flying. Birds also have feathers that make flight easier. Long feathers on the wings and tail help birds balance and steer and other feathers provide insulation and protect birds from the sun’s ultraviolet rays.

How have birds evolved for flight?

The Ground-Up Theory said that ancestors of birds ran along the ground, jumping into the air. Wings and feathers then evolved to aid them in propulsion, and flight evolved (Feduccia 2001a, Gill 1995). This theory is linked closely with the Dinosaur theory described above.