Bird wing
Bird wingsare a pairedforelimbinbirds.The wings give the birds theability to fly,creatinglift.
Terrestrialflightless birdshave reduced wings or none at all (for example,moa). Inaquatic flightless birds(penguins), wings can serve asflippers.[1]
Anatomy
[edit]Like most othertetrapods,the forelimb of birds consists of theshoulder(with thehumerus), theforearm(with theulnaand theradius), and the hand.
The hand of birds is substantially transformed: some of its bones have been reduced, and some others have merged with each other. Three bones of themetacarpusand part of thecarpal bonesmerge into acarpometacarpus.The bones of three fingers are attached to it. The frontmost one bears analula—a group of feathers that act like the slats of an airplane. Usually, this finger has onephalanx bone,the next has two, and the back has one (but some birds have one more phalanx on the first two fingers—the claw).
Finger identity problem
[edit]
The bones of three fingers are preserved in the bird wing. The question of which fingers they are has been discussed for about 150 years, and an extensive literature is devoted to it.[2][3]The anatomical, paleontological, and molecular data suggests that these are fingers 1–3, but embryological data suggests that these are actually fingers 2–4.[1]Several hypotheses have been proposed to explain this discrepancy. Most likely, in birds, finger buds 2–4 began to follow the genetic program for the development of fingers 1–3.[3]
Wing shape
[edit]
The shape of the wing is important in determining the flight capabilities of a bird. Different shapes correspond to different trade-offs between advantages such as speed, low energy use, and maneuverability.[4][5]
Two important parameters are theaspect ratioandwing loading.Aspect ratio is the ratio ofwingspanto the mean of itschord(or the square of the wingspan divided by wing area). Wing loading is the ratio of weight to wing area.
Most kinds of bird wings can be grouped into four types, with some falling between two of these types. These types of wings are elliptical wings, high-speed wings, high aspect ratio wings and soaring wings with slots.
Elliptical wings
[edit]Elliptical wings are rounded and short. This type of wing allows for tight maneuvering in confined spaces such as dense vegetation. Elliptical wings are common in forest raptors (such asAccipiterhawks), and manypasserines,particularly non-migratory ones (migratory species have longer wings). They are also common in species that use a rapid takeoff to evade predators, such aspheasantsandpartridges.
High speed wings
[edit]High-speed wings are short, pointed wings that when combined with a heavy wing loading and rapid wingbeats provide an energetically expensive, but high-speed flight. This type of wing is present in fast-flying birds such asducks.Birds that use their wings to "fly" underwater such as theauksalso have small and elongated wings.
The peregrine falcon has the highest recorded dive speed of 242 mph (389 km/h). Peregrine falcons have relatively large wings but they partially close their wings during dives. The fastest straight, powered flight is thespine-tailed swiftat 105 mph (170 km/h).
High aspect ratio wings
[edit]High aspect ratio (elongated) wings confer high flight efficiency for flights of long duration. When combined with a low wing loading, they are used for slow flight. This may take the form of almost hovering (as used bykestrels,ternsandnightjars) or in soaring andglidingflight, particularly thedynamic soaringused byseabirds,which takes advantage of wind speed variation at different altitudes (wind shear) above ocean waves to provide lift. Low-speed flight is also important for birds that plunge-dive for fish.
Soaring wings with deep slots
[edit]These wings are favored by larger species of inland birds, such aseagles,vultures,pelicans,andstorks.The slots at the end of the wings, between the primaries, reduce theinduced dragandwingtip vorticesby "capturing" the energy in air flowing from the lower to upper wing surface at the tips,[6]whilst the shorter size of the wings aids in takeoff (high aspect ratio wings require a longtaxito get airborne).[6]
References
[edit]- ^abVargas, A. O.; Fallon, J. F. (2005). "The Digits of the Wing of Birds Are 1, 2, and 3. A Review".Journal of Experimental Zoology Part B: Molecular and Developmental Evolution.304(3) (Journal of Experimental Zoology Part B: Molecular and Developmental Evolution ed.): 206–219.doi:10.1002/jez.b.21051.PMID15880771.
- ^Baumel, J. J. (1993).Handbook of Avian Anatomy: Nomina Anatomica Avium.Cambridge: Nuttall Ornithological Club. pp. 45–46, 128.
- ^abYoung, R. L; Bever, G. S.; Wang, Z.; Wagner, G. P. (2011)."Identity of the avian wing digits: Problems resolved and unsolved".Developmental Dynamics.240(5) (Developmental Dynamics ed.): 1042–1053.doi:10.1002/dvdy.22595.PMID21412936.S2CID37372681.
- ^Norberg, U. M. (1990).Vertebrate Flight: Mechanics, Physiology, Morphology, Ecology and Evolution.Berlin.ISBN978-3-642-83848-4.OCLC851392205.
{{cite book}}:CS1 maint: location missing publisher (link) - ^Pennycuick, C. J. (2008).Modelling the flying bird.Amsterdam: Academic.ISBN978-0-12-374299-5.OCLC272383165.
- ^abTucker, Vance (July 1993)."Gliding Birds: Reduction of Induced Drag by Wing Tip Slots Between the Primary Feathers".Journal of Experimental Biology.180:285–310.doi:10.1242/jeb.180.1.285.
