Information about Remex

The term flight feather refers to any of the long stiff feathers on the wing or tail of a bird; those on the wing are called remiges (singular remex) while those on the tail are called rectrices (singular rectrix). These feathers lack the insulating "aftershaft" found on contour feathers. They are asymmetrical, with the rachis running closer to the distal side of the feather, a shape which allows each flight feather to act as an individual airfoil, improving the generation of lift across wings and tail. The flexibility of the remiges on the wingtips of large soaring birds also allows for the spreading of those feathers, which helps to reduce the creation of wingtip vortices, thereby reducing drag.

Remiges

Remiges are attached to the rear side of the wing; the long calami, or quills, are deeply imbedded into the bones themselves. Corresponding remiges on individual birds are symmetrical between the two wings, matching to a large extent in size and shape (except in the case of mutation, damage or fluctuating asymmetry), though not necessarily in pattern.^[1][2] They are given different names depending on their position along the wing.

Primaries

Primaries are connected to the manus (carpometacarpus and phalanges); these are the longest and narrowest of the remiges (particularly those attached to the manus), and they can be individually rotated. These feathers are especially important for flapping flight, as they are the principal source of thrust, moving the bird forward through the air. Most thrust is generated on the downstroke of flapping flight. However, on the upstroke (when the bird often draws its wing in close to its body), the primaries are separated and rotated, reducing air resistance while still helping to provide some thrust.^[3] In soaring flight, large birds with broad wings spread their primaries to help reduce the turbulence created by wingtip vortices; this helps to decrease drag.^[4]

Species vary somewhat in the number of primaries they possess. The number in non-passerines generally varies between nine and 11,^[4] but grebes, storks and flamingos have 12,^[4] and ostriches have 16.^[4] While most modern passerines have ten primaries,^[4] some have only nine. Those with nine are missing the most distal primary (sometimes called the remicle) which is typically very small and sometimes rudimentary in passerines.^[4]

The outermost primaries—those connected to the phlanges—are sometimes known as pinions.

Secondaries

Secondaries are connected to the ulna. These feathers remain close together in flight (they cannot be individually separated like the primaries can) and help to provide lift by creating the airfoil shape of the bird's wing. Secondaries tend to be shorter and broader than primaries, with blunter ends (see illustration). They vary in number from a mere six in hummingbirds to as many as 40 in some species of albatross.^[4] In general, larger (and longer-winged) species have a larger number of secondaries.^[5] Birds in more than 40 non-passerine families seem to be missing the fifth secondary feather on each wing, a state known as diastataxis.^[7] In these birds, the fifth set of secondary covert feathers does not cover any remex, possibly due to a twisting of the feather papillae during embryonic development.^[7] Loons, grebes, pelicans, hawks and eagles, cranes, sandpipers, gulls, parrots, and owls are among the families missing this feather.

Tertials

Tertials are connected to the humerus in some species. These elongated "true" tertials act as a protective cover for all or part of the folded primaries and secondaries, and don't qualify as flight feathers as such.^[8] However, many authorities use the term tertials to refer to the shorter, more symmetrical innermost secondaries of passerines (which perform the same function as true tertials do) in an effort to distinguish them from the other secondaries.

Emargination

The outermost primaries of large soaring birds, particularly raptors, often show a pronounced narrowing at some variable distance along the feather edges. These narrowings are called either notches or emarginations depending on the degree of their slope.^[7] An emargination is a gradual change, and can be found on either side of the feather. A notch is an abrupt change, and is only found on the wider trailing edge of the remige. (Both are visible on the primary in the photo showing the feathers; they can be found about halfway along both sides of the left hand feather—a shallow notch on the left, and a gradual emargination on the right.) The presence of notches and emarginations creates gaps at the wingtip; air is forced through these gaps, increasing the generation of lift.^[9]

Alula

Feathers on the alula or bastard wing are not generally considered to be flight feathers in the strict sense; though they are asymmetrical, they lack the length and stiffness of most true flight feathers. However, alula feathers are definitely an aid to slow flight. These feathers—which are attached to the bird's "thumb" and normally lie flush against the anterior edge of the wing—function in the same way that the forward slot on an airplane wing does, increasing the speed of the airflow over the wing and thereby increasing lift. By manipulating its thumb to create a gap between the alula and the rest of the wing, a bird can avoid stalling when flying at low speeds or landing.^[7]

Remex development in nestling Hoatzins

The development of the remiges (and alula) of nestling Hoatzins is much delayed compared to the development of these feathers in other young birds, presumably because young Hoatzins are equipped with claws on their first two digits. They use these small rounded hooks to grasp branches when clambering about in trees, and feathering on these digits would presumably interfere with that functionality. Most youngsters shed their claws sometime between their 70^th and 100^th day of life, but some retain them—though callused-over and unusable—into adulthood.^[10][11]

Rectrices

Rectrices, which help the bird to brake and steer in flight, lie in a single horizontal row on the rear margin of the anatomical tail. Only the central pair are attached (via ligaments) to the tail bones; the remaining rectrices are imbedded into the rectricial bulb, a complex structure of fat and muscle that surrounds those bones. Rectrices are always paired, with a vast majority of species having six pairs. They are absent in grebes and some ratites, and greatly reduced in size in penguins.^{[4][12][13][14]} Many grouse species have more than 12 rectrices; some (including Ruffed Grouse and Hazel Grouse) have a number that varies between individuals.^[15] Domestic pigeons have a highly variable number, due to centuries of selective breeding.^[16]

Flight feather numbering conventions

In order to make the discussion of such topics as moult processes or body structure easier, ornithologists assign a number to each flight feather. By convention, the numbers assigned to primary feathers always start with the letter P (P1, P2, P3, etc.), those of secondaries with the letter S, those of tertials with T and those of rectrices with R.

Most authorities number the primaries descendantly, starting from the innermost primary (the one closest to the secondaries) and working outwards; others number them ascendantly, from the most distal primary inwards.^[4] There are some advantages to each method. Descendant numbering follows the normal sequence of most birds' primary moult. In addition, in the event that a species is missing the small distal 10^th primary, as some passerines are, its lack doesn't impact the numbering of the remaining primaries. Ascendant numbering, on the other hand, allows for uniformity in the numbering of non-passerine primaries, as they almost invariably have four attached to the manus regardless of how many primaries they have overall. ^[4] This method is particularly useful for indicating wing formulae, as the outermost primary is the one with which the measurements begin.

Secondaries are always numbered ascendantly, starting with the outermost secondary (the one closest to the primaries) and working inwards.^[4] Tertials are also numbered ascendantly, but in this case, the numbers continue on consecutively from that given to the last secondary (e.g. ... S5, S6, T7, T8, ... etc.).^[4]

Rectrices are always numbered from the centermost pair outwards in both directions.^[18]

Specialized flight feathers

The flight feathers of some species have undergone evolutionary changes which allow them to provide additional functionality.

In some species, for example, either remiges or retrices make a sound during flight. These sounds are most often associated with courtship or territorial displays. The outer primaries of male Broad-tailed Hummingbirds produce a distinctive high-pitched trill, both in direct flight and in power-dives during courtship displays; this trill is diminished when the outer primaries are worn, and absent when those feathers have been moulted.^[19] During the Northern Lapwing's zigzagging display flight, the bird's outer primaries produce a humming sound.^[20] The outer primaries of the male American Woodcock are shorter and slightly narrower than those of the female, and are likely the source of the whistling and twittering sounds made during his courtship display flights.^[21] Male Club-winged Manakins use modified secondaries to make a clear trilling courtship call. A curve-tipped secondary on each wing is dragged against an adjacent ridged secondary at high speeds (as many as 100 times per second—twice as fast as a hummingbird's wingbeat) to create a stridulation much like that produced by some insects.^[22] Both Wilson's and Common Snipe have modified outer tail feathers which make noise when they are spread during the birds' roller coaster display flights; as the bird dives, wind flows through the modified feathers and creates a series of rising and falling notes, which is known as "winnowing".^[23] Differences between the sounds produced by these two former conspecific subspecies—and the fact that the outer two pairs of rectrices in Wilson's Snipe are modified, while only the single outermost pair are modified in Common Snipe—were among the characteristics used to justify their splitting into two distinct and separate species.

Flight feathers are also used by some species in visual displays. Male Standard-winged and Pennant-winged nightjars have modified P2 primaries (using the descendant numbering scheme explained above) which are displayed during their courtship rituals.^[24] In the Standard-winged Nightjar, this modified primary consists of an extremely long shaft with a small "pennant" (actually a large web of barbules) at the tip. In the Pennant-winged Nightjar, the P2 primary is an extremely long (but otherwise normal) feather, while P3, P4 and P5 are successively shorter; the overall effect is a broadly-forked wingtip with a very long plume beyond the lower half of the fork.



Males of many species, ranging from the widely introduced Ring-necked Pheasant to Africa's many whydahs, have one or more elongated pairs of rectrices, which play an often-critical role in their courtship rituals. The outermost pair of rectrices in male lyrebirds are extremely long and strongly curved at the ends. These plumes are raised up over the bird's head (along with a fine spray of modified uppertail coverts) during his extraordinary display. Rectrix modification reaches its pinnacle among the birds of paradise, which display an assortment of often bizarrely modified feathers, ranging from the extremely long plumes of the Ribbon-tailed Astrapia (nearly three times the length of the bird itself) to the dramatically coiled twin plumes of the Magnificent Bird of Paradise.

Owls have remiges which are serrated rather than smooth on the leading edge. This adaptation disrupts the flow of air over the wings, eliminating the noise that airflow over a smooth surface normally creates, and allowing the birds to fly silently.^[25]

The rectrices of woodpeckers are proportionately short and very stiff, allowing them to better brace themselves against tree trunks while feeding. This adaptation is also found, though to a lesser extent, in some other species that feed along tree trunks, including woodcreepers and treecreepers.

Scientists have not yet determined the function of all flight feather modifications. For instance, male swallows in the genera Psalidoprocne and Stelgidopteryx have tiny recurved hooks on the leading edges of their outer primaries, but the function of these hooks is not yet known; some authorities suggest they may produce a sound during territorial or courtship displays.^[26]

Flight feathers in flightless birds

Over time, a small number of bird species have lost their ability to fly. Some of these, such as the flightless steamer ducks, show no appreciable changes in their flight feathers. Some, such as the Titicaca Flightless Grebe and a number of the flightless rails, have a reduced number of primaries.^[27]

The remiges of ratites are soft and downy; they lack the interlocking hooks and barbules that help to stiffen the flight feathers of other birds. In addition, the Emu's remiges are proportionately much reduced in size, while those of the cassowaries are reduced both in number and structure, consisting merely of 5–6 bare quills. Most ratites have completely lost their rectrices; only the Ostrich still has them.

Penguins have lost their differentiated flight feathers. As adults, their wings and tail are covered with the same small, stiff, slightly curved feathers as are found on the rest of their bodies.

The ground-dwelling Kakapo, which is the world's only flightless parrot, has remiges which are shorter, rounder and more symmetrically vaned than those of parrots capable of flight; these flight feathers also contain fewer interlocking barbules near their tips.^[28]

Flight feathers and moult

Once they have finished growing, feathers are essentially dead structures. Over time, they become worn and abraded, and need to be replaced. This replacement process is known as moult (molt in the United States). The loss of wing and tail feathers can affect a bird's ability to fly (sometimes dramatically) and in certain families can impair the ability to feed or perform courtship displays. The timing and progression of flight feather moult therefore varies between families.

For most birds, moult begins at a certain specific point, called a focus (plural foci), on the wing or tail and proceeds in a sequential manner in one or both directions from there. For example, most passerines have a focus between the innermost primary (P1, using the numbering scheme explained above) and outermost secondary (S1), and a focus point in the middle of the center pair of rectrices.^[29] As passerine moult begins, the two feathers closest to the focus are the first to drop. When replacement feathers reach roughly half of their eventual length, the next feathers in line (P2 and S2 on the wing, and both R2s on the tail) are dropped. This pattern of drop and replacement continues until moult reaches either end of the wing or tail. The speed of the moult can vary somewhat within a species. Some passerines that breed in the Arctic, for example, drop many more flight feathers at once (sometimes becoming briefly flightless) in order to complete their entire wing moult prior to migrating south, while those same species breeding at lower latitudes undergo a more protracted moult.^[30]



In many species, there is more than one focus along the wing. Here, moult begins at all foci simultaneously, but generally proceeds only in one direction. Most grouse, for example, have two wing foci: one at the wingtip, the other between feathers P1 and S1. In this case, moult proceeds descendantly from both foci. Many large, long-winged birds have multiple wing foci.

Birds that are heavily "wing-loaded"—that is, heavy-bodied birds with relatively short wings—have great difficulty flying with the loss of even a few flight feathers. A protracted moult like the one described above would leave them vulnerable to predators for a sizeable portion of the year. Instead, these birds lose all their flight feathers at once. This leaves them completely flightless for a period of three to four weeks, but means their overall period of vulnerability is significantly shorter than it would otherwise be. Eleven families of birds, including loons, grebes and most waterfowl, have this moult strategy.

Arboreal woodpeckers, which depend on their tails—particularly the strong central pair of rectrices—for support while they feed, have a unique tail moult. Rather than moulting their central tail feathers first, as most birds do, they retain these feathers until last. Instead the second pair of rectrices (both R2 feathers) are the first to drop. (In some species in the genera Celeus and Dendropicos, the third pair is the first dropped.) The pattern of feather drop and replacement proceeds as described for passerines (above) until all other rectrices have been replaced; only then are the central tail rectrices moulted. This provides some protection to the growing feathers, since they're always covered by at least one existing feather, and also ensures that the bird's newly strengthened tail is best able to cope with the loss of the crucial central rectrices. Ground-feeding woodpeckers, such as the wrynecks, do not have this modified moult strategy; in fact, wrynecks moult their outer tail feathers first, with moult proceeding proximally from there.

Age differences in flight feathers

There are often substantial differences between the remiges and rectrices of adults and juveniles of the same species. Because all juvenile feathers are grown at once—a tremendous energy burden to the developing bird—they are softer and of poorer quality than the equivalent feathers of adults, which are moulted over a longer period of time (as long as several years in some cases).^[31] As a result, they wear more quickly.

In general, juveniles have feathers which are narrower and more sharply-pointed at the tip.^[32][33] This can be particularly visible when the bird is in flight, especially in the case of raptors. The trailing edge of the wing of a juvenile bird can appear almost serrated, due to the feathers' sharp tips, while that of an older bird will be straighter-edged.^[32] The flight feathers of a juvenile bird will also be uniform in length, since they all grew at the same time. Those of adults will be of various lengths and levels of wear, since each is moulted at a different time.^[31]

The flight feathers of adults and juveniles can differ considerably in length, particularly among the raptors. Overall, juveniles tend to have slightly longer rectrices, and shorter, broader wings (with shorter outer primaries, and longer inner primaries and secondaries) than do adults of the same species.^[31] However, there are many exceptions. In longer-tailed species, such as Swallow-tailed Kite, Secretary bird and European Honey Buzzard, for example, juveniles have shorter rectrices than adults do. Juveniles of some Buteo buzzards have narrower wings than adults do, while those of large juvenile falcons are longer.

Experts theorize that the differences help young birds compensate for their inexperience, weaker flight muscles and poorer flying ability.^[33]

Wing formula

A wing formula describes the shape of distal end of a bird's wing in a mathematical way. It can be used to help distinguish between species with similar plumages, and thus is particularly useful for those who ring (band) birds.^[7]

To determine a bird's wing formula, the distance between the tip of the most distal primary and the tip of its greater covert (the longest of the feathers that cover and protect the shaft of that primary) is measured in millimeters. In some cases, this results in a positive number (e.g., the primary extends beyond its greater covert), while in other cases it's a negative number (e.g. the primary is completely covered by the greater covert, as happens in some passerine species). Next, the longest primary feather is identified, and the differences between the length of that primary and that of all remaining primaries and of the longest secondary are also measured, again in millimeters. If any primary shows a notch or emargination, this is noted, and the distance between the feather's tip and any notch is measured, as is the depth of the notch. All distance measurements are made with the bird's wing closed, so as to maintain the relative positions of the feathers.

While there can be considerable variation across members of a species—and while the results are obviously impacted by the effects of molt and feather regeneration—even very closely related species show clear differences in their wing formulas.^[7]

Primary extension

The distance that a bird's longest primaries extend beyond its longest secondaries (or tertials) when its wings are folded is referred to as the primary extension or primary projection.^[35] As with wing formulae, this measurement is useful for distinguishing between similarly plumaged birds; however, unlike wing formulae, it isn't necessary to have the bird in-hand to make the measurement. Rather, this is a useful relative measurement—some species have long primary extensions, while others have shorter ones. Among the Empidonax flycatchers of the Americas, for example, the Dusky Flycatcher has a much shorter primary extension than does the very similarly-plumaged Hammond's Flycatcher.^[35] Europe's Common Skylark has a long primary projection, while that of the near-lookalike Oriental Skylark is very short.^[36]

Citations

References

• id="CITEREFBostwickPrum2005">Bostwick, Kimberly S. & Richard O. Prum (2005), "Courting Bird Sings with Stridulating Wing Feathers", Science 309 (5735), <[1]
  • id="CITEREFCampbellLack1985">Campbell, Bruce & Elizabeth Lack, eds. (1985), A Dictionary of Birds, Carlton, England: T and A D Poyser, ISBN 0-85661-039-9
    • id="CITEREFCleereNurney1998">Cleere, Nigel & Dave Nurney (1998), Nightjars: A Guide to Nightjars and Related Nightbirds, Mountfield, East Sussex: Pica Press, ISBN 1-873403-48-8
      • id="CITEREFdel HoyoElliottSargatal1992">del Hoyo, Josep; Andrew Elliott & Jordi Sargatal, eds. (1992), Handbook of the Birds of the World, vol. 1, Barcelona: Lynx Edicions, ISBN 84-87334-10-5
        • id="CITEREFdel HoyoElliottSargatal1997">del Hoyo, Josep; Andrew Elliott & Jordi Sargatal, eds. (1997), Handbook of the Birds of the World, vol. 4, Barcelona: Lynx Edicions, ISBN 84-87334-22-9
          • id="CITEREFdel HoyoElliottChristie2004">del Hoyo, Josep; Andrew Elliott & David Christie, eds. (2004), Handbook of the Birds of the World, vol. 9, Barcelona: Lynx Edicions, ISBN 84-87334-69-5
            • id="CITEREFEhrlichDobkinWheyePimm1994">Ehrlich, Paul R.; Darryl A. Dobkin & Darryl Wheye et al. (1994), The Birdwatcher's Handbook, Oxford University Press, ISBN 0-19-858407-5
              • id="CITEREFFerguson-LeesChristie2001">Ferguson-Lees, James & David A. Christie (2001), Raptors of the World, London: Christopher Helm, ISBN 0-7136-8026-1
                • id="CITEREFForsman1999">Forsman, Dick (1999), The Raptors of Europe and the Middle East, London: T and A D Poyser, ISBN 0-85661-098-4
                  • id="CITEREFHowell2002">Howell, Steve N. G. (2002), Hummingbirds of North America, London: Academic Press, ISBN 0-12-356955-9
                    • id="CITEREFJenniWinkler1994">Jenni, Lukas & Raffael Winkler (1994), Moult and Ageing of European Passerines, London: Academic Press, ISBN 0-12-384150-X
                      • id="CITEREFKaufman1990">Kaufman, Kenn (1990), Advanced Birding, Boston: Houghton Mifflin, ISBN 0-395-53376-7
                        • id="CITEREFLivezey2005">Livezey, Bradley C. (2005), "Morphological corollaries and ecological implications of flightlessness in the kakapo (Psittaciformes: Strigops habroptilus)", Journal of Morphology 213 (1): 105-145, <[2]
                          • id="CITEREFMadgeMcGowan2002">Madge, Steve & Phil McGowan (2002), Pheasants, Partridges & Grouse, London: Christopher Helm, ISBN 0-7136-3966-0
                            • id="CITEREFMollerHoglund1991">Moller, Anders Pape & Jacob Hoglund (1991), "Patterns of Fluctuating Asymmetry in Avian Feather Ornaments: Implications for Models of Sexual Selection.", Proceedings: Biological Sciences 245 (1312): 1-5
                              • id="CITEREFPaulson2005">Paulson, Dennis (2005), Shorebirds of North America, London: Christopher Helm, ISBN 0-7136-7377-X
                                • id="CITEREFSibley2001">Sibley, David (2001), The Sibley Guide to Bird Life & Behaviour, London: Christopher Helm, ISBN 0-7136-6250-6
                                  • id="CITEREFSvenssonGrant1999">Svensson, Lars & Peter J. Grant (1999), Collins Bird Guide: The Most Complete Field Guide to the Birds of Britain and Europe, London: HarperCollins, ISBN 0-00-219728-6
                                    • id="CITEREFTaylorvan Perlo1998">Taylor, Barry & Ber van Perlo (1998), Rails, London: Christopher Helm, ISBN 1-873403-59-3
                                      • id="CITEREFTrail2001">Trail, Pepper (2001), Wing Feathers, U.S. Fish and Wildlife Service, <[3] (retrieved on 2007-05-22)

                                        See also

                                        • Bird anatomy
                                        • Bird flight
                                        • Pinioning
                                        • Plumage

                                        External links

                                        • Wing Feathers - US Fish and Wildlife Service document Contains excellent photographic examples of emargination and notching in raptor remiges.
                                        • Video of feeding Magellanic Woodpecker (Campephilus magellanicus) Shows use of rectrices for bracing.
                                        • Video of singing male Superb Lyrebird (Menuta novaehollandiae) Shows long modified rectrices which are used in display (though the video doesn't show full display).
                                        • Video of male Club-winged Manakin (Machaeropterus deliciosus) Shows use of secondary remiges to produce sound.
                                        • Cornell Laboratory of Ornithology's American Woodcock (Scolopax minor) recordings #94216 has a good example of the sounds made by remiges during courtship display flight, starting at about 2:32.
                                        • Sound made by rectrices in courtship flight of Common Snipe (Gallinago gallinago)

                                        •  • [ e] Birds
                                        Anatomy	Skeleton - Flight - Eggs - Feathers - Plumage
                                        Evolution	Archaeopteryx - Enantiornithes - Hybridisation - Late Quaternary prehistoric birds - Fossils - Taxonomy - Extinction
                                        Behaviour	Singing - Intelligence - Migration - Reproduction - Incubation - Brood parasites
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                                        Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds. They are the outstanding characteristic that distinguishes the Class Aves from all other living groups. Other Theropoda also had feathers (see Feathered dinosaurs).
                                        ..... Click the link for more information.
                                        WING
                                        
                                        City of license Dayton, Ohio
                                        Broadcast area Dayton
                                        Branding "ESPN 1410"
                                        Slogan Same as branding
                                        First air date 1921
                                        Frequency 1410 KHZ
                                        Format Sports Talk
                                        ERP 5,000 watts-D/N
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                                        The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals and birds.
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                                        Aves
                                        Linnaeus, 1758
                                        
                                        Orders
                                        
                                        About two dozen - see section below
                                        
                                        Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals.
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                                        Pennaceous feathers are also known as contour feathers and are present in most modern birds and in some species of maniraptoran dinosaurs.
                                        
                                        Pennaceous feathers have a central shaft (or rachis) with vanes branching off to either side.
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                                        rachis (pronounced /ˈɹeɪkɪs/) is the main axis of the inflorescence, or spike, of wheat and other cereals, to which the spikelets are attached. It is also the part of the axis that the pinnae are attached to in ferns, the main stem of a compound leaf (such as in
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                                        In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. Non-scientists often wonder why zoological and human anatomists use complex terminology to describe locations on a body, when common terms like "up",
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                                        The lift force, lifting force or simply lift is a mechanical force generated by solid objects as they move through a fluid.^[1]
                                        
                                        While many types of objects can generate lift, the most common and familiar object in this category is the airfoil, a
                                        ..... Click the link for more information.
                                        Verification of the Origins of Rotation in Tornadoes Experiment or VORTEX, is a field project that seeks to understand how a tornado is produced by deploying around 18 vehicles that are equipped with customized instruments used to measure and analyze the weather around a
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                                        drag (sometimes called resistance) is the force that resists the movement of a solid object through a fluid (a liquid or gas). Drag is made up of friction forces, which act in a direction parallel to the object's surface (primarily along its sides, as friction forces at the
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                                        Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals.
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                                        mutations are changes to the base pair sequence of the genetic material of an organism. Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or viruses, or can occur deliberately
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                                        In evolutionary psychology, symmetry especially facial symmetry is one of a number of traits, including averageness and youthfulness, associated with health, physical attractiveness and beauty of a person or non-human animal.
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                                        The manus (Latin for 'hand') is the zoological term for the distal portion of the fore limb of an animal. In tetrapods, it is the part of the pentadactyl limb that includes the metacarpals and digits (phalanges).
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                                        Phalanges is commonly given to the bones that form fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.
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                                        Flight is the main mode of locomotion used by most of the world's bird species. It assists birds while feeding, breeding and avoiding predators.

                                        Evolution and purpose of bird flight

                                        
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                                        Thrust is a reaction force described quantitatively by Newton's Second and Third Laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a proportional but opposite force on that system.
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                                        Ciconiidae
                                        Gray, 1840
                                        
                                        Genera
                                        
                                        See text.
                                        Storks are large, long-legged, long-necked wading birds with long stout bills, belonging to the family Ciconiidae.
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                                        Phoenicopteriformes
                                        Fürbringer, 1888
                                        
                                        Family: Phoenicopteridae
                                        Bonaparte, 1831
                                        
                                        Genus: Phoenicopterus
                                        Linnaeus, 1758
                                        
                                        Flamingos (
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                                        Struthionidae
                                        Vigors, 1825
                                        
                                        Genus: Struthio
                                        Linnaeus, 1758
                                        
                                        Species: S.
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                                        Passeriformes
                                        Linnaeus, 1758
                                        
                                        Suborders
                                        

                                        • Acanthisitti
                                        • Tyranni
                                        • Passeri
                                          

                                        
                                        
                                        A passerine is a bird of the giant order Passeriformes. More than half of all species of bird are passerines.
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                                        The ulna (elbow bone) is a long bone, prismatic in form, placed at the medial side of the forearm, parallel with the radius.

                                        Articulations

                                        The ulna articulates with:

                                        • the humerus, at the right side elbow as a hinge joint.

                                        
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                                        Trochilidae
                                        Vigors, 1825
                                        
                                        Subfamilies
                                        
                                        Phaethornithinae
                                        Trochilinae
                                        
                                        For a taxonomic list of genera, see:

                                        • List of hummingbirds in taxonomic order

                                        For an alphabetic species list, see:

                                        • Alphabetic species list
                                          

                                        
                                        
                                        
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                                        Diomedeidae
                                        G.R. Gray, 1840
                                        
                                        Genera
                                        
                                        Diomedea
                                        Thalassarche
                                        Phoebastria
                                        Phoebetria
                                        
                                        Albatrosses, of the biological family Diomedeidae
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                                        Passeriformes
                                        Linnaeus, 1758
                                        
                                        Suborders
                                        

                                        • Acanthisitti
                                        • Tyranni
                                        • Passeri
                                          

                                        
                                        
                                        A passerine is a bird of the giant order Passeriformes. More than half of all species of bird are passerines.
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