Bird Feather Development

ings are highly modified arms that, through their unique structure and shape, enable most birds to fly. There are many types of wings; they vary by species. For instance, penguins, which are flightless, use their wings for the specialized task of swimming. Among all wings that have existed in the animal kingdom, those of birds are the best for flying. Their wings are light and durable, and in some cases their shape and effectiveness can be modified during flight. To understand the relationship between wings and a bird's weight, the concept of wing loading, which helps explain the type of flight for each species, is useful.

Wings in the Animal Kingdom

^^ Wings have always been modified ^^ arms, from the first models on pterosaurs to those on modern birds. Wings have evolved, beginning with the adaptation of bones. Non-avian wings have a membranous surface composed of flexible skin. They extend from the bones of the hand and body usually down to the legs, depending on the species. Avian wings, on the other hand, are based on a very different principle: the arm and hand form a complex of skin, bone, and muscle, with a wing surface consisting of feathers. Furthermore, the avian wing allows for important changes in form, depending on the bird's adaptation to the environment.

still had talons, and only one finger extended their wings.

Four fingers extend the membrane, and the thumb remained as a talon.

The fused fingers form the tip of the wing where the rectrices, or primary feathers, are attached.

Types of Wings

^^ According to the environment in which they live and the type of flight they ^ perform, birds have different wing shapes that allow them to save energy and to perform efficiently during flight. The wing shape also depends on the bird's size. Consequently, the number of primary and secondary feathers changes depending on the needs of a given species.

Hiere are many secondary feathers.

Short feathers are located all over the wing.

The external primary feathers are longer.

The outermost primary feathers are shorter than the central ones.

The external primary feathers are longer.

They are wide at the base, with separate feather tips.

Remiges are large and tight to allow for flapping; the surface is reduced to prevent excessive friction.

Functional for mixed flights, they are very maneuverable. Many birds have them.

They are wide at the base, with separate feather tips.

WINGS FOR SOARING ABOVE LAND

Hiere are many secondary feathers.

Short feathers are located all over the wing.

WINGS FOR SOARING ABOVE LAND

Wide, they are used to fly at low speeds. The separate remiges prevent turbulence when gliding.

WINGS FOR SOARING ABOVE THE OCEAN

Their great length and small width make them ideal for gliding against the wind, as flying requires.

In adapting to swimming, the feathers of penguins became short, and they serve primarily as insulation.

The Upturned Wing Tip Soaring Birds

RADIUS

HUMERUS

CORACOID

WANDERING ALBATROSS

Wing Size and Loading

^^ The wingspan is the ^^ distance between the tips of the wings. Together with width, it determines the surface area, which is an essential measurement for bird flight. Not just any wing can support any bird. There is a close relationship between the animal's size (measured by weight) and the surface area of its wings. This relationship is called wing loading, and it is crucial in understanding the flight of certain species. Albatrosses, with large wings, have low wing loading, which makes them great gliders, whereas hummingbirds have to flap their small wings intensely to support their own weight. The smaller the wing loading, the more a bird can glide; the bigger, the faster a bird can fly.

ARGENTA VIS

MAGNIFICENS

(extinct)

x LARGER FINGER fP— SMALLER FINGER >—— CARPOMETACARPUS

- ALULAR DIGIT

Controls the alula, a

\ feathered projection on the front edge of the wing. ULNA

PRIMARY COVERTS

They cover the remiges and, with the alula, change the wing shape at will.

PRIMARIES

They are in charge of propulsion; they are also called remiges.

MEDIAN WING COVERTS

They change the wing's lift when they rise slightly.

GREATER WING COVERTS

They create more surface area and cover the intersection point y of the tertiaries. /

r SECONDARIES

Their number varies greatly depending on the species. They complete the surface.

TERTIARIES

Together with the secondaries, they create the wing's surface.

STERNUM OR KEEL

Flightless Wings

^^ Among these, penguins' wings are an extreme ^ case of adaptation: designed for rowing underwater, they work as fins. On running birds, wings' first and foremost function is to provide balance as the bird runs. These wings are also related to courtship, as birds show off their ornamental feathers during mating season by opening their wings or flapping them. Wings are also very efficient at controlling temperature, as birds use them as fans to ventilate their bodies.

FUNCTION The wings of ostriches carry out the functions of balancing, temperature regulation, and courtship.

LOOSE FEATHERS Sometimes barbicels are missing, and feathers on the wing come apart, creating a loose and ruffled appearance.

PRIMARY FEATHERS Flying birds have from nine to 12 primary feathers. Running birds may have up to 16.

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To Renew Is to Live

The periodic renewal of plumage is called molting. It is the replacement of worn-out, older feathers with new ones that are in better condition. In a bird's life cycle, molting is as important an event as migrating or caring for young. The beginning of this phenomenon is determined by environmental factors that trigger a series of hormonal stimuli in birds: they start to eat more and to decrease their other activities. This, in turn, causes them to gain weight through an accumulation of fat that will serve as the £

source of energy for developing new plumage.

Plumage Molting

The main function of molting is to replace worn-out plumage. It also helps the bird adapt its appearance to the seasons and to different stages in life. The renewal can be partial or total. Some feathers are replaced before the spring, when the task is to attract a partner for reproductive purposes. In the fall, before birds have to start caring for their young, the renewal is complete. On most birds, molting takes place in each pteryla, following a determined order. Penguins, however, renew all their feathers at the same time, within two to six weeks.

SEASONAL CHANGE

In the high mountains, snow transforms the landscape during winter. During this time, nonmigratory birds exchange their summer plumage for a winter one. This change helps them to protect themselves from predators.

DERMAL PAPILLAE

A feather develops in each of them.

Order of Replacement

^^ Many species start ^^ molting, a process triggered by hormones, in a specific order. Molting starts with remiges and wing coverts, continues with rectrices, and finishes with body coverts. This gradual process keeps the body temperature stable.

Remiges Feathers

Renewal starts in the first primary remiges and spreads outward. In the secondary remiges, it spreads in two directions. Replacement occurs when the new remiges are three fourths developed.

Massive replacement of chest, back, and head coverts occurs from the center outward. This change coincides with the substitution of the seventh remex (singular of remiges).

Rectrices are replaced from the center outward. This happens simultaneously with the loss of tertiary remiges.

The wing coverts are replaced.

OLD FEATHER

Renewing the plumage is important because it helps keep the bird's body temperature stable. It also keeps the feathers in place while the bird moves about, and it helps the bird to go unnoticed by predators.

THE PERCENTAGE OF A BIRD'S BODY COVERED BY FEATHERS WHEN RENEWAL IS AT ITS PEAK

DEVELOPING PLUMAGE

Renewal starts in the first primary remiges and spreads outward. In the secondary remiges, it spreads in two directions. Replacement occurs when the new remiges are three fourths developed.

DERMAL PAPILLAE

A feather develops in each of them.

BLOOD VESSELS

nourish the feathers during their development.

NEW FEATHER BEING FORMED

SUMMER PLUMAGE

The feathers have deep pigmentation. This helps birds blend in with the vegetation.

WINTER PLUMAGE

The new, unpigmented feathers make it possible for ptarmigans to blend with the white snow.

DEVELOPING PLUMAGE

BLOOD VESSELS

nourish the feathers during their development.

NEW FEATHER BEING FORMED

Bird Dermal Papillae

A papilla develops from skin cells. The epidermal cells multiply faster than the dermal ones and form a collar-shaped depression called the follicle.

EPIDERMAL COLLAR

In the epidermal papilla, the formation of the new feather causes the detachment of the worn-out one.

A papilla develops from skin cells. The epidermal cells multiply faster than the dermal ones and form a collar-shaped depression called the follicle.

EPIDERMAL COLLAR

The papilla grows and becomes layered. The outermost layer is covered with keratin, which protects the underlying Malpighian layer (nucleus of the papilla). A group of dermal cells brings nutrients through the blood vessels that travel along the new feather.

Massive replacement of chest, back, and head coverts occurs from the center outward. This change coincides with the substitution of the seventh remex (singular of remiges).

Rectrices are replaced from the center outward. This happens simultaneously with the loss of tertiary remiges.

The wing coverts are replaced.

Dermal Wings

The rapid growth of the Malpighian layer starts to develop the new feather. The rachis, barbs, and barbules become keratinized. The vessels that bring nutrients are reabsorbed, and the connection with the dermic layer is closed. Finally the protective vane breaks, and the feather unfurls.

The feather, now lifeless, assumes its characteristic blade shape. A residue of dermal and epidermal cells at the base of the follicle forms an area that will allow for replacement when the feather wears out.

20 days

IS THE AVERAGE AMOUNT OF TIME THAT IT TAKES FOR A NEW FEATHER TO FORM.

Gliding

Marine Birds

Involves using air currents to fly and save energy when traveling long distances. There are two types of gliders, terrestrial birds and marine birds, each of which is adapted to different atmospheric phenomena. Terrestrial birds rise on thermals (rising air currents). Marine birds make use of oceanic surface winds. Once the birds gain altitude, they glide off in straight paths. They slowly lose altitude until encountering another thermal that will lift them. Both terrestrial and marine gliders have wings of considerable size.

Dynamic soaring is performed by birds with long and thin wings, such as the albatross. These wings are designed to take advantage of horizontal air currents, which are responsible for the formation of waves in the ocean. The result is a flight consisting of a series of loops as the bird is lifted upward when it faces the wind and moved forward when it faces away from the wind. This kind of flight can be performed at any time.

FLIGHT PATTERNS

Flying in formation is a way for birds in flapping flight to save energy. The leader encounters more resistance as it flies, while the others take advantage of its

Relay

When the leader gets tired, another bird takes its position.

Relay

When the leader gets tired, another bird takes its position.

TYPES OF GLIDING FEATHERS

Terrestrial Glider

A large wing surface allows it to make the most of rising air currents at moderate speed.

Marine Glider

Thin and long wings allow it to make the most of the constant surface winds and offer less resistance to forward movement.

Terrestrial Glider

A large wing surface allows it to make the most of rising air currents at moderate speed.

Takeoff

Usually, a powerful jump followed by the vertical flapping of the wings is enough to make a bird take flight. As it descends, the tip feathers are stacked on top of each other, forming an airtight surface that helps drive the bird upward. As the bird raises its wings to repeat the movement, the feathers curve and open until the wing reaches its highest point. With a couple of flaps of the wings, the bird is in flight. Bigger birds need a running start on the ground or water in order to take off.

Bird Flapping Motion

During the upward movement in wing flapping, the primary feathers open up, offering less resistance to the air.

THE PERCENTAGE OF WING FLAPPING THAT GEESE SPARE THEMSELVES BY FLYING IN FORMATION

SPEED OF DISPLACEMENT

depends on the strength of the headwind.

Marine Birds

FLIGHT PATTERNS

Flying in formation is a way for birds in flapping flight to save energy. The leader encounters more resistance as it flies, while the others take advantage of its

Bird Watching Log Sheet

THE PERCENTAGE OF WING FLAPPING THAT GEESE SPARE THEMSELVES BY FLYING IN FORMATION

SPEED OF DISPLACEMENT

depends on the strength of the headwind.

wake. There are two basic patterns: "L" and "V." The first is used by pelicans, and the second is used by geese.

form the tip.

Ascent

When birds find a warm air current, they gain height without having to flap their wings.

Straight Gliding

Once the maximum possible height is gained, the birds glide in straight paths.

Descent

The birds slowly glide downward.

wake. There are two basic patterns: "L" and "V." The first is used by pelicans, and the second is used by geese.

"L" FORMATION Leader

The leader makes the most effort, as it "parts" the air.

The Rest of the Formation

The other birds make use of the turbulence produced by the leader's flapping to gain height, following along behind.

"V" FORMATION

The principle is the same, but the birds form two lines that converge at a point. This is the usual formation used by geese, ducks, and herons.

SECONDARY FEATHERS

There are many of these because of the wing's length.

The wing length of some pelicans may reach 8 feet (240 cm) from tip to tip.

PRIMARY FEATHERS

There are fewer of these, as they only

UPPER SIDE

Convex. The air covers more distance and accelerates, causing a lower pressure that "sucks" the wing upward.

LOWER SIDE

Concave. The air covers less distance, it does not accelerate, and its pressure does not change.

form the tip.

WINGLETS

Terrestrial gliders usually have separate primary feathers (toward the tip of the wing) that serve to decrease the noise and tension generated there by the passing of air. Modern airplanes copy their design.

The tip feathers work as airplane winglets.

TERRESTRIAL BIRDS

They use warm, rising air currents generated through convection in the atmosphere or through the deflection of air currents against crags or mountains. Then they glide in a straight flight path. This type of flight is possible only during the day.

Ascent

When birds find a warm air current, they gain height without having to flap their wings.

Thermal: Hot Air

Straight Gliding

Once the maximum possible height is gained, the birds glide in straight paths.

Descent

The birds slowly glide downward.

Bird With Pine Feather Blog

Ascent

They rise again when they encounter another warm air current.

Ascent

They rise again when they encounter another warm air current.

Airplane Winglets are made of one or several pieces.

Thermal: Hot Air

African Grey Parrot Plane
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