1. Kā noturēties gaisā?
Guna Doķe

3. Kādēļ ziloņiem ir plakanas pēdas?

4. Kādēļ ziloņiem ir plakanas pēdas?
Jo viņi krīt no kokiem

5. Kādēļ ziloņiem ir plakanas pēdas?
Jo viņi krīt no kokiem
Kādēļ ziloņiem ir plakanas ausis?

6. Kādēļ ziloņiem ir plakanas pēdas?
Jo viņi krīt no kokiem
Kādēļ ziloņiem ir plakanas ausis?
Jo viņi ne vienmēr piezemējas uz kājām

7. Krišana

8. Krišana F1 – spēks m – masa g – brīvās krišanas paātrinājums
g = 9.8 m/s2 =

9. Krišana F2 – spēks Cd – plūsmas pretestības koeficients
(bezdimensionāls)
ρ – gaisa blīvums
v – krišanas ātrums
S – saskares laukums
The drag coefficient is a number that aerodynamicists use to model all of the complex dependencies of shape, inclination,and flow conditions on aircraft drag.
F1 – spēks
m – masa
g – brīvās krišanas paātrinājums
g = 9.8 m/s2 =

10. Kā noturēt ziloni gaisā?
Pirmais Ņūtona likums, jeb inerces likums: ja uz ķermeni neiedarbojas citi ķermeņi vai arī, ja to iedarbība ir savstarpēji pretēja, ķermenis saglabā miera vai vienmērīgas taisnvirziena kustības stāvokli.

11. Kādēļ zilonis krīt ātrāk nekā pele?
Ziloņa smaguma spēks ir ievērojami lielāks nekā peles smaguma spēks
Lai panāktu situāciju F1 = F2 nepieciešams lielāks krišanas ātrums
Ziloņa kustība tiek paātrināta ilgāk
Nemainīgais krišanas ātrums ir lielāks → zilonis ātrāk sasniedz zemi
The elephant and the feather are each being pulled downward due to the force of gravity. When initially dropped, this force of gravity is an unbalanced force. Thus, both elephant and feather begin to accelerate (i.e., gain speed). As the elephant and the feather begin to gain speed, they encounter the upward force of air resistance. Air resistance is the result of an objectplowing through a layer of air and colliding with air molecules. The more air molecules which an object collides with, the greater the air resistance force. Subsequently, the amount of air resistance is dependent upon the speed of the falling object and the surface area of the falling object. Based on surface area alone, it is safe to assume that (for the same speed) the elephant would encounter more air resistance than the feather.
But why then does the elephant, which encounters more air resistance than the feather, fall faster? After all doesn't air resistance act to slow an object down? Wouldn't the object with greater air resistance fall slower?Answering these questions demands an understanding of Newton's first and second law and the concept of terminal velocity. According to Newton's laws, an object will accelerate if the forces acting upon it are unbalanced; and further, the amount of acceleration is directly proportional to the amount of net force (unbalanced force) acting upon it. Falling objects initially accelerate (gain speed) because there is no force big enough to balance the downward force of gravity. Yet as an object gains speed, it encounters an increasing amount of upward air resistance force. In fact, objects will continue to accelerate (gain speed) until the air resistance force increases to a large enough value to balance the downward force of gravity. Since the elephant has more mass, it weighs more and experiences a greater downward force of gravity. The elephant will have to accelerate (gain speed) for a longer period of time before there is sufficient upward air resistance to balance the large downward force of gravity.
Once the upward force of air resistance upon an object is large enough to balance the downward force of gravity, the object is said to have reached a terminal velocity. The terminal velocity is the final velocity of the object; the object will continue to fall to the ground with this terminal velocity. In the case of the elephant and the feather, the elephant has a much greater terminal velocity than the feather. As mentioned above, the elephant would have to accelerate for a longer period of time. The elephant requires a greater speed to accumulate sufficient upward air resistance force to balance the downward force of gravity. In fact, the elephant never does reach a terminal velocity; the animation above shows that there is still an acceleration on the elephant the moment before striking the ground. If we were to depict the relative magnitude of the two forces acting upon the elephant and the feather at various times in their fall, perhaps it would appear as shown below. (NOTE: The magnitude of the force vector is indicated by the relative size of the arrow.)
Observe from the above diagrams and the above animation that the feather quickly reaches a balance of forces and thus a zero acceleration (i.e., terminal velocity). On the other hand, the elephant never does reach a terminal velocity during its fall; the forces never do become completely balanced and so there is still an acceleration. If given enough time, perhaps the elephant would finally accelerate to high enough speeds to encounter a large enough upward air resistance force in order to achieve a terminal velocity. If it did reach a terminal velocity, then that velocity would be extremely large - much larger than the terminal velocity of the feather.
So in conclusion, the elephant falls faster than the feather because it never reaches a terminal velocity; it continues to accelerate as it falls (accumulating more and more air resistance), approaching a terminal velocity yet never reaching it. On the other hand, the feather quickly reaches a terminal velocity. Not requiring much air resistance before it ceases its acceleration, the feather obtains the state of terminal velocity in an early stage of its fall. The small terminal velocity of the feather means that the remainder of its fall will occur with a small terminal velocity.

12. Kā noturēt ziloni gaisā (ilgāk)?
Palielinot saskares laukumu!

13. Izpletņu tipa lidošana/krišana dzīvnieku pasaulē
Dažādi zirnekļi
Sifaka
Indris
Galagos
Saki pērtiķi
Kaķi (nosacīti)
u.c.
Par izpletņa tipa lidošanu uzkata procesu, kad kritiens uz leju notiek leņķī ne mazākā 45 grādi pret horizontu
Par izpletņa tipa lidošanu uzkata procesu, kad kritiens uz leju notiek leņķī ne mazākā 45 grādi pret horizontu

14. Planēšana

15. Planēšana
Smaguma spēks
(F = mg)
Planēšanas virziens

16. Gaisa pretestības radīts,
Planēšana
«Berzes» spēks
Gaisa pretestības radīts,
parādās pretēji
planēšanas virzienam
Smaguma spēks
(F = mg)
Planēšanas virziens

17. Planēšana parādās pretēji Cēlējspēks planēšanas virzienam
«Berzes» spēks
Gaisa pretestības radīts,
parādās pretēji
planēšanas virzienam
Cēlējspēks
Rodas gaisa plūsmas un
planētāja aerodinamiskās
uzbūves mijiedrbības rezultātā
(sīkāks apskats teorijas
daļā)
Smaguma spēks
(F = mg)
Planēšanas virziens

18. Cēlējspēks Virs spārna: lielāks ātrums → mazāks spiediens
An explanation of lift frequently encountered in basic or popular sources is the equal transit-time theory. Equal transit-time states that because of the longer path of the upper surface of an airfoil, the air going over the top must go faster in order tocatch up with the air flowing around the bottom, i.e. the parcels of air that are divided at the leading edge and travel above and below an airfoil must rejoin when they reach the trailing edge. Bernoulli's Principle is then cited to conclude that since the air moves faster on the top of the wing the air pressure must be lower. This pressure difference pushes the wing up.[71]
Virs spārna: lielāks ātrums → mazāks spiediens
→ parādās cēlējspēks
Zem spārna: mazāks ātrums → lielāks spiediens

19. Planēšana – kā viņi to dara I
Ādas kroka ķermeņa sānos starp priekšējām un pakaļējām ekstremitātēm, vai pat līdz astes galam
Planējošo varžu gadījumā, ādas membrānas ar lielu virsmas laukumu ir starp pirkstiem

20. Video Gliding snake: http://www.youtube.com/watch?v=3vhgC_g1cmU

21. Planēšana – kā viņi to dara II
Pielāgojot savu ķermeņa formu!
«Lidojošā» čūska izplešs savas ribas un iegūst ķermeņa formu, kas palielina saskares
laukumu un atbilst nosacījumiem, lai parādītos cēlējspēks
Planējošās skudras, krītot no kokiem, maina sava ķermeņa formu, lai varētu mainīt
kritiena ātrumu un trajektoriju un nokļūt atpakaļ uz koka stumbra
These are un-winged ants that fall into a very specific subset of requirements, like having good eyesight, living in rain forests that flood, and forage for food at the ends of branches. They also tend to be armored. When they fall from trees, they focus on the lighter color of the trunk against the darker forest background, and then flatten their head, legs and abdomen and then glide from free-fall to a J-shaped flight, and then grasp the tree. The whole thing seems to have developed as a way to avoid falling out of trees and being eaten on the forest floor. Gliding ants have an 85% greater chance of falling and landing on a tree than ants that just fall. Read more:  Read more at 

22. Planēšana – kā viņi to dara III
Spuras kalpo kā spārni
Var noplanēt līdz pat 400 m un sasniegt ātrumu 7 km/h
Maksimālais augstums virs jūras līmeņa 6 m
In May 2008, a Japanese television crew (NHK) filmed a flying fish (dubbed "Icarfish") off the coast of Yakushima Island, Japan. The creature spent 45 seconds in flight.[11] The previous record was 42 seconds.[11]
Flying fish can use updrafts at the leading edge of waves to cover distances of at least 400 m (1,300 ft).[8] They can travel at speeds of more than 70 kilometres per hour (43 mph).[9] Maximum altitude is 6 m (20 ft) above the surface of the sea.[10] Some accounts have them landing on ships' decks.
The transition of predominantly swimming locomotion directly to flight has evolved in a single family of marine fish called Exocoetidae. Flying fish are not true fliers in the sense that they do not execute powered flight. Instead, these species glide directly over the surface of the ocean water without ever flapping their "wings." Flying fish have evolved abnormally large pectoral fins that act as airfoils and provide lift when the fish launches itself out of the water. Additional forward thrust and steering forces are created by dipping the hypocaudal (i.e. bottom) lobe of their caudal fin into the water and vibrating it very quickly, in contrast to diving birds in which these forces are produced by the same locomotor module used for propulsion  

23. Planēšana – kā viņi to dara IV
Izmantojot siltās gaisa plūsmas
Trajectory or flight path of a Peregrine Falcon superimposed on a black and white satellite map of the area (southeast Hungary).  Color indicates vertical velocity, with more reddish color indicating climbing within thermals and bluish color indicating sinking  (i.e., periods of gliding between thermals)
Thermal soaring 
  Thermals are generated by rising columns of warm air that develop over differentially heated surfaces during the day and are the domain of birds with high lift slotted wings. The shorter wings of these birds, give them better turning characteristics that make them better able to stay within the confines of small thermals. This form of soaring is used by a number of larger species during migration where they climb within a thermal to gain altitude before gliding down to the next thermal and climbing once more. As thermals are generally not developed over large water masses birds tend to collect in huge numbers in places like Gibraltar where they try to obtain as much altitude as they can to help them negotiate the straights into Africa beyond. 
  Thermals are commonly used by vultures who do not take to the wing until the sun has heated the ground long enough to allow the production of rising air columns. 
The soaring flights of vultures and hawks depend upon vertical hot-air currents called thermals. Such currents are not continuous updrafts or downdrafts originating from a specific spot; instead, as a local region of the ground is heated, a vertical, hot-air updraft is created. At the top of the column, a thermal bubble is formed by the hot air curving outward, downward, and then around the bubble. It is then pinched off by cool air flowing into the column and floats upward. The free-floating thermal bubble is doughnut shaped, with the air rising in the centre and cycling outward and downward. Soaring birds spiral downward in the updraft; however, because the bubble rises faster than birds descend, soaring birds are carried upward, but at a speed less than that of the bubble. When a bird reaches the bottom of the bubble, it begins a straight gravitational glide until it reaches the next thermal bubble. Thus, static soaring in a thermal bubble can be recognized by its alternating flight pattern of circling and straight gliding.

24. Planēšana – kā viņi to dara V
Dažādas putnu sugas izmanto augšupejošas gaisa plūsmas,
kas rodas gaisa masām saskaroties ar:
Klintīm
Kalniem
Ēkām
Viļņiem
Obstruction lift
Over the sea, large physical objects and thermal updrafts are very rare. Instead, Albatrosses and their kin use small local updrafts caused by the wind meeting the waves. These updrafts are small and temporary, so sea birds fly close to the sea's surface, often riding along one wave catching the air that rises over it before switching quickly to another. In this way, their flight is a zigzag from one lot of rising air to the next.
Slope soaring 
  Slope soaring occurs where winds meet an obstruction and are forced to rise over them. This rising air provides the lift for a large number of different bird species and is particularly noticeable when watching Kestrels hunting along the sea cliffs where large amounts of uplift are developed. Normally they have to hover when hunting, but in these conditions they can often remain motionless bouyed up by the rising air.

25. Planēšana – kā viņi to dara VI
  Dynamic soaring is carried out by sea birds over water where no thermals or slopes are available to provide free lift. This is a more complicated affair than the other two forms of soaring and relies on a birds ability to convert momentum into altitude. For this reason birds with high aspect wings are by far the most proficient at this soaring technique and the albatross with its huge wingspan and high weight is the perfect practitioner. 
  Dynamic soaring relies on a gradient of wind speed being produced over the water. This occurs as energy is lost from wind in the production of waves close to the water surface, so close to the water the wind is moving more slowly. 
  The bird starts by gaining altitude, flying against the wind. Once it is high enough it starts to glide downward. With the wind behind it it rapidly picks up speed and when it gets close to the water it turns into the wind. The air near the water is slower than above and it quickly passes through this with the decrease in drag produced by the slower moving air. The bird then rises quickly on the wind which is now head on. The wind increases the airspeed over its wings and so provides lift that the bird exploits until its airspeed comes close to a stall. It then turns smartly and heads down wind once more gaining speed as it goes. Using this technique sea birds are able to cover huge tracts of the ocean.
Unlike static soaring, which is done at relatively high altitudes over land, dynamic soaring is done at low levels and is usually restricted to oceanic areas. Dynamic soaring depends upon a steady horizontal sea wind, which is laminated into layers of different velocities because of the frictional interaction between the water and the air; the lower layers have the lowest velocity. The flight path of a bird performing dynamic soaring tends to be a series of inclined loops that are perpendicular to the direction of the wind. A soaring albatross, for example, will begin its gravitational glide approximately 15 metres (50 feet) above the sea. Because it glides downwind, its velocity is increased both by descent and by the wind at its tail. As the bird nears the sea, it makes a turn into the wind, and the forward flight velocity derived from the downwind glide and the tail wind combine to lift the albatross slowly back to its initial gliding height, but with a loss of horizontal velocity. The bird therefore turns downwind again and begins to repeat the soaring cycle.
Because it depends upon the presence of a horizontal air current, the flight of flying fish is more akin to soaring than to true flying. As a flying fish approaches the water surface, its pectoral and pelvicfins, which are analogous to the forelimbs and hind limbs of quadrupeds, are pressed along the side of the body. The greatly enlarged, winglike pectoral fins then spread out as the fish leaves the water. The wind against the fins provides lift to raise the body above the water, and the tail continues to undulate to provide additional thrust. When the entire body is out of the water, the enlarged pelvic fins extend, and the fish glides for a short distance until its forward velocity is lost. Occasionally, as a fish drops back into the water, it will undulate its tail to initiate another short flight.

26. Bet ja nepietiek arī ar to...
Nepieciešami kustīgi spārni (vai jebkas cits , kas var kalpot kā dzinējs)

27. Lidošana Dzinējspēks!! Smaguma spēks Cēlējspēks
Rodas spārnu kustības rezultātā
«Berzes» spēks
Smaguma spēks

28. Spārnu kustība un dzinējspēks
(A) Depictions of the vortex-ring and continuous-vortex gaits. (B) Cross-sectional view of the wing profile. Lift produced during flapping provides weight support (upward force) and thrust (horizontal force). In the vortex-ring gait, lift is produced only during the downstroke, providing positive upward force and forward thrust. In the continuous-vortex gait, lift is produced during both the upstroke and the downstroke. The downstroke produces a positive upward force and forward thrust; the upstroke produces a positive upward force and rearward thrust. Partial flexion of the wing during the upstroke reduces the magnitude of the rearward thrust to less than that of the forward thrust produced during the downstroke, providing net positive thrust per wingbeat (From Hedrick et al. 2002).
Birds are known to employ two different gaits in flapping flight, a vortex-ring gait in slow flight and a continuous-vortex gait in fast flight. In the vortex ring gait, the upstroke is aerodynamically passive (there is no bound circulation during this phase, and hence no trailing vortex), and the wings flex and move close to the body to minimize drag. In the continuous vortex gait (where each wingtip sheds a separate vortex trail during both the upstroke and downstroke), the wings are aerodynamically active throughout (i.e., lift is generated both during the downstroke and the upstroke), while the wings remain near-planar throughout and deform only by flexure at the wrist. Hedrick et al. (2002) studied the use of these gaits over a wide range of speeds in Cockatiels and Ringed Turtle-doves trained to fly in a wind tunnel. Despite differences in wing shape and wing loading, both species shifted from a vortex-ring to a continuous-vortex gait at a speed of 7 meters/sec. They found that the shift from a vortex-ring to a continuous-vortex gait depended on sufficient forward velocity to provide airflow over the wing during the upstroke similar to that during the downstroke. This shift in flight gait appeared to reflect the need to minimize drag and produce forward thrust in order to fly at high speed.
Flight is produced by the simultaneous rotation of the left and right wings in a circle or in a figure eight. This rotation produces the upward thrust, or lift, necessary to overcome gravity and the forward thrust required to overcome drag. As the downward and backward phase of rotation forces the air backward and the body forward, lift is produced by the unequal velocities of the air across the upper and lower wing surfaces.
Putni pamatā izmanto 2 veidu spārnu kustības:
gredzenveida - virpuļu (lēnam lidojumam)
nepārtrauktas - virpuļu (ātram lidojumam)

29. Spārnu forma
Spārna formu viegli raksturot kā spārna garuma un platuma attiecību (putniem šī attiecība var būt no 1.5 līdz pat 18)
Putniem, kas izmanto planēšanu vai arī tiem,
kam nepieciešama spēja uzņemt lielu atrumu
Aspect ratio affects the relative magnitude of induced and profile drag; if mass, wing area, and other wing shape parameters remain constant, a long, thin high-aspect ratio wing reduces the cost of flight and extends range. However, high aspect ratio is not necessarily associated with high speed (favored by smaller wings). Elliptical wings (low aspect ratio) can maximize thrust from flapping, whereas as more pointed wing (high-speed) with a sharp wingtip minimizes wing weight and wing inertia. Short wings must be flapped at high frequency to provide sufficient thrust. So, relatively short, pointed wings allow rapid wing-beats with reduced inertia and that translates into greater speed (e.g., shorebirds, auks, and ducks). More rounded (convex) wings produce more lift toward the wingtip (where the wing moves faster) and are particularly effective for birds that fly at slow speeds (e.g., taking off from the ground) or need high levels of acceleration. Many small passerines often fly slowly or in 'cluttered' habitats, or need rapid acceleration to escape predators. The same is true for birds like accipiters and corvids (crows and jays; Lockwood et al. 1998).
A convenient way to describe the shape of a wing is by its aspect ratio - the ratio of length to width. Among bird wings, aspect ratios vary from about 1.5 to as high as about 18. Elliptical (or 'rapid takeoff') wings (above) have relatively low aspect ratios, while high speed wings & soaring wings have high aspect ratios.The long (or soaring) wings of birds with very high aspect ratios, like albatrosses, generate lots of lift, while the narrow, pointed shape helps reduce drag while gliding (because the small area of the pointed tip minimizes pressure differences and, therefore, turbulence at the wing tip).
High speed wings, like those of falcons, swallows, & swifts, have relatively high aspect ratios. These narrow, tapering wings can be flapped rapidly to generate lots of speed with minimal drag (because, again, the small area of the pointed tip minimizes pressure differences and turbulence at the wing tip).
Parasti dažādiem dziedātājputniem,
dzeņiem, u. c. putniem, kam
nepieciešams lidināties starp
kokiem un spēt izdarīt asus
pagriezienus

30. Putna svara – spārnu laukuma attiecība (raksturo slodzi uz spārniem)
Vel viens lidošanas spēju aprakstošs lielums ir putna svara – spārnu laukuma attiecība
Putniem, kuriem šī attiecība ir zema, nepieciešams mazāk jaudas, lai lidotu
Another important factor that influences a bird's flying ability is wing loading - the weight (or mass) of a bird divided by wing area (grams/total wing area in square centimeters). Birds with low wing loading need less power to sustain flight. Birds considered to be the 'best' flyers, such as swallows & swifts, have lower wing loading values than other birds. 
Different combinations of wing loading and aspect ratio permit particular flight modes and foraging strategies. Species with long wings and high aspect ratios also have low wing loadings, particularly those with low body mass, and their flight is inexpensive, e.g., many seabirds, swifts, and swallows. Birds with high wing loading and short wings, but still with high aspect ratios, are adapted to fast and rather inexpensive flight (short wings reduce profile power that is large in fast flight), e.g., loons, mergansers, geese, swans, ducks, and auks. Birds flying close to or among vegetation, e.g., flycatchers, tend to have low aspect ratios that contribute to high induced drag, but their low mass and wing loading reduce flight costs. The very low aspect ratios of many smaller birds that occupy densely-vegetated habitats, e.g., gallinaceous birds, mean that the energetic cost of flight is expensive, so these species spend much of their time walking. Birds with higher wing loading, e.g., penguins, are flightless (Norberg 2002).

31. Flight styles -- Based on differences in aspect ratios and wing loading (Rayner 1988; see figure below), flight styles can also be categorized as either specialized or non-specialized. The non-specialists have average aspect ratios and average wing loading and are excellent flyers (capable of long flights and with good maneuverability) that typically use flapping flight. The non-specialists can be further subdivided, based on aspect ratio and speed, as slow non-specialists and fast non-specialists. In the slow category would be most passerines (Passeriformes), pelicans (Pelicaniformes), herons, egrets, ibises, and storks (Ciconiiformes), pigeons and doves (Columbiformes), cuckoos (Cuculiformes), most owls (Strigiformes), trogons (Trogoniformes), most birds in the order Gruiformes (e.g., gallinules, rails, and bustards), mousebirds (Coliiformes), woodpeckers (Piciformes), and parrots (Psittaciformes). Fast non-specialists include many falcons (Falconidae), gulls (Larinae), and storm-petrels (Hydrobatidae).
Birds with morphological attributes (aspect ratio and wing loading) that differ (beyond one or two standard deviations) from those of ‘typical’ birds exhibit specialized flight styles (Rayner 1988). Among these specialized styles are:
(1) Marine soarers are birds that fly for long periods over the open ocean and have very high aspect-ratio wings and average or low wing loading that reduce the energetic cost of flight. Birds in this category include the albatrosses (Procellariiformes).
(2) Divers/swimmers are birds with medium to high aspect ratios and high wing loading, including murres, loons, grebes, scoters, mergansers, ducks, and swans. These birds fly rapidly, but with limited maneuverability, characteristics useful for birds that often fly long distances (e.g., during migration or to feeding areas) and take-off and land on water where precise maneuverability is not as important.
(3) Aerial hunters are birds with high aspect-ratio wings and low wing loading, a combination permitting rapid flight and excellent maneuverability. Aerial hunters include swallows and martins (Passeriformes), swifts (Apodiformes), nightjars (Caprimulgiformes), Swallow-tailed Kites (Falconiformes), frigatebirds (Fregatidae), terns (Sterninae), some falcons (e.g., hobbies and Eleonora’s Falcon), and tropicbirds (Phaethontidae).
(4) Soarers/coursers include birds with low aspect ratios and low wing loading, characteristics that allow relatively large birds to either soar or fly just above the vegetation in open habitats in search of prey. Birds in the soaring category include hawks and eagles (Falconiformes), vultures, condors, and storks (Ciconiiformes), and cranes (Gruiformes). Coursing birds include some owls (e.g., Barn Owl and Short-eared Owl; Strigiformes) and harriers (Falconiformes).
(5) Short-burst fliers are birds with low aspect ratios and high wing loading that fly infrequently and only for short distances. Birds in this category include those in the orders Galliformes (e.g., turkeys, pheasants, quail, grouse, and megapodes) and Tinamiformes (tinamous).
(6) Hoverers are birds capable of flying in one position without wind and have high aspect ratios and, surprisingly, high wing loading. The high aspect ratio reduces the energetic cost of flight, whereas the high wing loading permits relatively fast, agile flight (Rayner 1998). The only true hoverers are the hummingbirds (Apodiformes).

32. Spalvu nozīme Palīdz izvairīties no virpuļu rašanās , samazina to
Once they are in the air, birds move forwards by flapping their wings.The stroke down and towards the back pushes them through the air. The feathers on the outer half of the wing (the primaries) move vertically through the air on the downstroke. They have the effect of little propellers, pushing the bird forward. The effect of the airstream over the upper and lower wing surfaces holds the bird up.
At low speeds (such as during take-off & landing), birds can maintain smooth air flow over the wing (and, therefore, maintain lift) by using the alula (also called the bastard wing). The alula is formed by feathers (usually 3 or 4) attached to the first digit. 
When these feathers are elevated (above right & below right), they keep air moving smoothly over the wing & help a bird maintain lift.
t increasing angles of attack, an eddy starts to propagate from the trailing edge towards the leading edge of the wing. As a result, air flowing over the top of the wing separates from the upper surface and lift is lost. However, when coverts are lifted upward by the eddy, they prevent the spread of the eddy and work as 'eddy-flaps.'
High-lift wings have lower aspect ratios & there are spaces between the feathers at the end of the wing. These 'slots' help reduce drag at slow speeds because the separated tip feathers (shown in the White Stork pictured below) act as 'winglets' and spread vorticity both horizontally and vertically.
Feathers make an ideal aerodynamic surface for airflow. They can produce a smooth uninterrupted surface over which air can pass freely and can remain flexible without losing their aerodynamic properties. Further to that, the surface is also somewhat malleable, giving under areas of pressure, thus letting air pass more easily over the body without disrupting flow and causing drag.  Flight feathers are asymmetrical, with the leading edge vane being narrower, thicker and less flexible than the trailing edge. If the leading edge of the feather was to bend excessively in the airflow it would cause twisting of the feather, leading to a damaging loss of lift. This asymmetry, however, also ensures that the trailing web of the feather bends upward during the downstroke, providing forward momentum and lift. It has also been shown that the outer primary feathers, that is the ones closest to the wing tip, are mechanically stronger than those closer to the wing root (Ennos, Hickson & Roberts, 1995). This is probably to property that helps them withstand the larger aerodynamic forces that these feathers are subjected to. 

33. Astes nozīme
Bird tails & flight -- Most birds have rather short triangular tails when spread. In flight, the tail is influenced by the time-varying wake of flapping wings and the flow over the body. It is reasonable to assume that body, wings and tail morphology have evolved in concert. Modelling the interaction between the wings and tail suggests that the induced drag of the wing–tail combination is lower than that for the wings alone. A tail thus enables the bird to have wings that are optimized for cruising speed (with the tail furled to minimize drag) and, at low speeds, the spread tail reduces induced drag during manoeuvring and turning flight. Observations show that tails are maximally spread at low speeds and then become furled increasingly with increasing speed (Hedenström 2002).
Figure to the left. Flow visualization around mounted wingless starling bodies using the smoke-wire technique in a wind tunnel at 9 ms−1. (a) The bird with intact tail and covert feathers; (b) tail feathers protruding beyond ventral coverts are trimmed to the same length as coverts; (c) tail feathers, ventral and dorsal covert feathers removed. The height of the wake increases from (a) to (c). The dorsal boundary layer also becomes increasingly turbulent in (b) and (c) compared with the intact tail-body configuration in (a). From: Hedenström (2002).
 The wings are not the only lifting surfaces found on birds, the tail also plays an important role in flight. Obviously tail types vary greatly within the birds and some tails are used for display as well as for flight, but like the wing, their shape is often influenced by their lifestyle.   The wings of a bird generally lie slightly ahead of the centre of gravity, this means that when a bird flies its posterior trails in the airflow behind it. The tail provides not only the lift required to buoy up the weight of the body but it also helps in flight control, unfortunately it also adds to drag at higher speeds. The tail allows the wing design in birds to be tailored for efficient cruising and high speed flight and under these conditions it is furled to provide minimal drag. At lower speeds, however, or during maneuvers the tail can be quickly unfurled to reduce induced drag (see later) from the wings and provide a surface for enhanced steering, lift or braking. The tail is suspected to play an important part in maintaining balance and stability in flight and it would seem that it is required to generate lift at low speed when the interaction between the wings and the tail can also most effectively reduce drag. 
  The retrices, or tail feathers generally number 10-12, but are found to range between 8 and 24. These are normally straight and bilaterally paired and the bases covered by coverts to produce a smooth surface for airflow. When you look at a birds tail you see the retrices which are controlled by the tail muscles that allow for the various movements that are required for precision flying.

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