Week 22 Flashcards

Question

Rachis- Barbs- Barbules and hooks-

Answer 1

Rachis: hollow, central shaft providing backbone. Barbs: extend either side; site of most pigments.- have small barbules radiating out from them. Are the site of most of the pigments. Barbules & hooks: create stiffness & flexibility; fasten feathers to one another. These little barbules and hooks link up together to create both a stiffness and a flexibility in the outer surface of the bird. Effectively they’re fastening their feathers to one another to create this continuous, streamlined surface. Preaning is partially used to restore any interlocking of these barbules and hooks that comes undone.

Answer 2

* Smaller than contour feathers- * Lack barbules and hooklets: not zipped together meaning that they are not locked together. * Soft and fluffy * Insulation- they are found closest to the skin of the bird, providing this insulating layer of warmth.

Answer 3

* Intermediate in shape between contour and down * Found between contour feathers * Help with insulation * Help keep form- fill out the body contours, it helps to keep the form in general.

Answer 4

* Hairlike: few barbs at tip * Covered by other feathers- not exposed, never found alone and are found next to contour feathers. * Pressure and vibration receptors- each flight feathers for example might have 8 to 12 filoplumes associated with it. also , unlike other feathers, they have no muscles at their base. But their follicles are endowed with abundant nerve ending, which are sensitive to changes in pressure and vibration. Effectively they are operating as these pressure and vibration receptors. * Help keep other feathers in order- act as sensory organ for keeping the other feathers, particularly the contour feathers in place and adjusting them in flight and for insulation and during things like bathing.

Answer 5

Whereas all birds have the other four types only some have bristle feathers. They are stiff feathers with a few barbs near the base. In those birds that have them, they tend to be found around the eyes and the mouth. They function as sort of guard hairs, protecting those vital organs. They might also act as some sort of sensory organ a bit like the whiskers of a cat. And in some birds, particularly those that catch insects on the wing, they might act as a funnel to funnel those invertebrates towards the beak, enhancing foraging behaviour. * Stiff, with a few barbs * Occur around eyes and mouth of some birds * Protective/filters * Funnels for insectivores

Answer 6

a species found in southern africa, each pair of sociable weavers, sometimes with a few little helpers, builds its own nest chamber. But these sociable weavers build collectively together and form these enormous colonies. They are so big sometimes, so many pairs contributing to this overall structure, each with their own next cavity that the weight of the nest can bring down trees or telegraph poles. Because there are lots of nests in the same place, this makes them really attractive to predators like these snakes who come searching for eggs or young chicks. Now the sociable weavers can attempt to chase off snakes, but they don't have anything other than the ability to mob and yell at them to try and get rid of them. They are aided in getting rid of snakes by pygmy falcons. Often you find a pair of pygmy falcons nesting in one of the chambers in these huge sociable weaver colonies and they eat snakes so they act as a protective force to the sociable weavers. Interspecific interaction.

Answer 7

provide colouration Crypsis Attraction Insulation Flight

Answer 8

* Blending into background to avoid detection * Predators sneaking up on prey * Prey escaping predators * Behavioural traits to match Cryptic colouration helps hide or camouflage the bird, lowering the likelihood that the individual will be noticed. Its helping them blend into the background to avoid detection for some reason. Some predatory birds have cryptic colouring that guarantees a more dependable approach to prey. For example the typical white colouring of the head, neck and underparts of many fish eating birds helps them to remain undetected by fish looking up into the bright sky. More commonly cryptic colouring is used to escape the attention of predators to avoid being eaten by something nasty. For these protective colourations to be effective, it is sometimes important for certain postures to be adopted and for the bird to remain immoble.

Answer 9

* Attract mates * Males usually brighter than females * Sexually selected trait * Brightest males picked by females Some birds have plumages designed to stand out from background and show off. They are generally used to attract mates. And in many species, its the males who are brightly coloured. That is because often it is females who are the choosy sex and males who are trying to attract selection. As such, this is a sexually selected trait found in one sex and not the other. So many species that have brightly coloured males, females are actually rather drab brown. Theres no need for them to show off. And they are actually better off being less conspicuous and less likely to be spotted by predators. In these species where males are displaying their wares through their plumage, its often the brightest coloured males who are picked by females. That may be inherent quality of the male, or it may be a good forager and able to collect more of these carotenoids that form the reds and oranges and yellows in the plumage.

Answer 10

* Primary force driving evolution of feathers * Vital for endothermy (body temp. c. 40°C) * Denser plumage in winter * Fluff out feathers in cold conditions Insulation is believed to be the primary force driving the evolution of feathers. As endothermic organisms birds maintain a constant body temperature, which can be as high as 40 degrees. The insulation provided by the feathers greatly reduces the amount of energy required to keep up the body heat. And in some birds they moult and have a denser plumage in winter, particularly those living in very cold environments. And just like with crypsis for example then these feather characteristics can be enhanced by behavioural traits. For instance, if you look out on a cold morning in winter here in the UK, you might see a bird looking rather fluffed up as it deals with those early morning temperatures.

Answer 11

Feathers are also important in flight, but initially evolved for insulation. So flight followed that initial evolution of veined feathers. Early forays by gliding and weak flapping flight probably fostered additional changes in feather form and function on the wings and the tail particularly. Feather design nowadays gives birds the strength, flexibility and rigidity to support themselves in the air, which of course provides very little support itself. Theres all sorts of characteristics about flight, not just feather form and function.

Answer 12

•Restore feather structure, clean plumage, rearrange feathers- depending on the type of maintenance of the bill is used in one of two ways. Either the feather is worked between the mandibles of the bill with a sort of nibbling action. Which is probably important for restoring the relationship between the barbules and the hooks. Relocking those feathers contour feathers together again and for removing dust particles and stale oils. Second way of manipulating in preening is where bills are wiped across the surface of the feather and thats probably important in rearranging them a little bit in drying them out or particularly in the application of preening oils.

Answer 13

•Apply oils from the uropygial gland for waterproofing- these oils come from something known as the uropygial gland and they are crucial for waterproofing the feathers. Not all parts of the body can be reached by a bird's beak, especially if that beak is a particular shape. Sometimes the head and neck are rubbed with the feet instead of the bill.

Answer 14

Feathers are fundamental to survival and so feather care is of the utmost importance. Because feathers are inert. And do not have an internal system of nourishment and maintenance. Left untended they would become brittle with age and exposure were it not for regular care, which includes the application of waxy secretions produced by the preen gland.

Answer 15

In certain species you also see whats known as Allopreening, thats where one individual preens another, either in turn or simultaneously. Studies have shown that although one function of Allopreening is hygienic, reaching bits of the body that an individual cant reach itself. This allopreening may well serve social functions as well.

Answer 16

Bathing is another behaviour that is used for feather care, although it is most commonly carried out with water, some birds such as pheasants, use dust instead

Answer 17

After bathing in water, the bird is in a particularly vulnerable condition as its flight efficiency is somewhat impaired. Therefore, it needs a nearby safe place in which to preen itself and to let the feathers dry.

Answer 18

mechanism to assist in body cooling in hot conditions.

Answer 19

In some species you also see this so called sunning behaviour, where the bird settles onto the ground in some relatively protected location. And exposes itself itself to the full sunlight, spreading out its wings and its tail. And often the bird is also fluffing out its feathers in this position. Sunning probably has several functions associated with feather care. One of those is that the sun’s heat is invaluable in restoring and maintaining the shape of the major flight feathers. Also, the interaction of sunlight with the preening oils may be important in synthesising vitamin D. the warmth of the sun may help the spread of preening oil on the feathers or of softening old oil to help their removal.

Answer 20

And finally, some may stimulate the activity of ectoparasites. Which can then be more easily spotted and picked off by the bird. In some cases theres also this rather intriguing behaviour known as anting. Which involves the bird squatting on the ground in an area where ants are common. The ants then run freely over the bird throughout the plumage, and its suggested that birds exploit the formic acid produced by many ants, which helps remove stale preening oil from the feathers. The ants may of course also be catching ectoparasites and helping hygiene in that regard.

Answer 21

Because feathers are subject to damage and wear. Despite all of the feathers care that goes on. Plumage effectiveness is only going to be maintained across time if damaged and worn out feathers can be replaced. And this occurs on a regular basis through a process known as moulting. Moulting is this replacing of old feathers with new ones. Now the number of times that happens per year varies from species to species or even within species, but it occurs at least once a year in all birds. It is an energetically costly process, and of course when you are missing some feathers then flight efficiency or otherwise is pampered. So moulting does not coincide with energetically other costly activities, or those requiring the feathers for good reason. So not when, say the birds are breeding or migrating. It would also be disastrous, of course, if all the feathers dropped off at once and had to be re grown. So if feathers are re places in an orderly predictable sequence and thats particularly true of those involved in flight, so the wing and the tail feathers. Moulting not only allows a bird to replace old feathers, but of course it allows a dramatic change in appearance. In some species where males are brightly coloured to attract females in the breeding season, what you find is that once they no longer need to be attracting females, males mouly into drab, cryptic plumage during the non breeding season and then moult back into their bright colourations at the start of their next breeding season. Replace old feathers with new ones 1+ times per year Lot of energy: not when breeding/migrating

Answer 22

orderly, predictable sequence – especially wing and tail feathers

Answer 23

Forelimbs modified as wings. And indeed, they have a particular shape known as an airfoil, which is critical for lift. All birds have feathered tails, that is they no longer unlike their reptilian ancestors, have bones in the tail, they just have feathers. They have a toothless horny beak, again unlike Archeopteryx for instance, they have no teeth because those are very heavy features, so they have lost those in terms of lightening for flight.

Answer 24

Maintenance of constant body temperature. Birds are of course endothermic, so they maintain a constant body temperature.

Answer 25

* High metabolic rate * Good insulation * characteristics shared with mammals

Answer 26

Advantage: live in extreme environments- very hot ones or cold ones, which is impossible for many ectotherms. Disadvantage: energetically expensive- you need to be eating all the time. The metabolic rate of birds is about 10 times that of amphibians and reptiles that need a constant source of fuel, so they have to eat much more.

Answer 27

Ancestor could fly But, NOT a defining avian characteristic Some birds have subsequently ‘lost’ flight The ancestor could fly to some extent, probably only weak flapping flight at best. But this is clearly not a defining avian characteristic. That is because other taxa can fly, think bats for e.g. and also that some birds have lost the ability to fly, like the brown kiwi. So although we think of flight and birds as being synonymous in many senses, its not a defining characteristic.

Answer 28

``` •Diversity –Size, plumage, habitat, mating systems, bills •Taxonomy –Reptiles, Archaeopteryx •Feathers –Characteristics, types, colouration, functions, care •Other avian features –NOT flight ```

Answer 29

Gliding has evolved on many occasions usually to aid canopy animals in getting from tree to tree. Gliding has particularly evolved among rainforest animals, especially in Asia where the trees are very tall and quite widely spaced. We see gliding in some Chinese gliding frogs for instance, in paradise tree snakes and in gliding ants. Also in flying squirrels, which glide between trees.

Answer 30

Have also been observed to glide often for up to hundred of metres on the drafts, on the edges of waves, with only their initial leap from the water to provide height. So gliding is pretty common in the natural world.

Answer 31

By contrast active flapping flight has only evolved in four main groups, the now extinct pterosaurs, bats, birds and insects. In many senses birds are the most specialised of these for flight. - -Bats - -Birds - -Insects - -Pterosaurs

Answer 32

Birds have a large number of adaptations for flapping flight. 1-feathers 2.lightening

Answer 33

Light Strong Streamlined Flexible

Answer 34

much lighter than the scales in which they evolved from.

Answer 35

in order to avoid snapping from all the forces being applied during flapping flight.

Answer 36

contour feathers can be locked together to form this ideal aerodynamic streamlined surface for air flow. In producing this smooth uninterrupted outer surface over which air can pass freely. Birds reduce whats known as the drag that would hold them back.

Answer 37

they give under pressure, thus letting air pass more easily over the body without disrupting the flow and causing excess drag. They are designed to maximise aerodynamic properties in changing conditions.

Answer 38

Skeleton Beak Reproduction

Answer 39

–Reduced number of bones- unnecessary bones have been lost- no bones in the tail and are now just made up of feathers. –Bones hollow and lack bone marrow- the remaining skeleton is made lighter than in other taxa because many bones are hollow, they are honeycombed with airspaces and strengthened by crisscrossing struts. They also lack bone marrow which is a heavy substance. Number of hollow bones varies from bird species to species. Diving birds for example dont have any hollow bones bc they need the weight, whie large gliding and soaring birds tend to have many hollow bones. The more efficient flyers seem to have more bones that are hollow. –Skull lost heavy jaw- birds skull is also extremely light relative to other taxonomic groups. Thats partly due to the elimination of a heavy jaw structure including big jaw muscles and also to the loss of teeth.

Answer 40

–Toothless- so they have a toothless beak now compared to archaeopteryx. Instead of teeth birds have a structure called the gizzard. Its a functional analogue of mammalian molars. A large strong muscular structure used primarily for grinding and digesting tough food, but its much lighter than teeth.

Answer 41

–Organs enlarged seasonally- only develop reproductive organs in the breeding season. Females have just one ovary and it increases by up to 1500 times in size when required. –Oviparous- that means they lay their eggs as soon as they are fully formed, the vast majority of embryonic development is done outside the female's body, thus saving her from carrying around the extra weight of developing young inside her.

Answer 42

As a consequence of the loss of certain bones, the hollowing of at least some of those that remain and the reduction in the weight of the skull, a pelican for e.g. which is approximately 5 feet long only weighs about 9kg of which the skeleton is only 650g. And we can contrast that to the otter which weighs much more.

Answer 43

–Fusion of bones to form rigid girders and platforms. –Wishbone- which is formed by fusion of the collarbones at their base, offers strong structural support for the wings and provides a brace during the powered stroke of flight. –Keel- And in flying birds the breast bone is fused to a deep keel. This longitudinal ridge of bone. That keel provides an anchor for the powerful flight muscles. The deeper the keel the more powerful the flight of that bird.

Answer 44

•Muscles- two main flight muscles attached to each wing. –Pectoralis (up to 35% total weight)- powers the downstroke of flight, thats the one that generates most of the propulsion. Its therefore portionally huge compared to other taxa. –Supracoracoideus- its much smaller than the pectoralis muscle and has a tendon which curves around to attach to the top of the humerus. Can provide power to the upstroke if required. But more usually its just a recovery stroke to get the wing back into the upward position for the powerful downward stroke. –48 other wing muscles- which are more subtle alterations in wing shape and form during flight and especially during takeoff and landing.

Answer 45

Main sense is sight- rather than smell which we see in most reptiles and mammals.

Answer 46

Large eyes Large brains- Ample processing centres- the brain expansion in birds relative to reptiles is of centres related to sight. The processing centres for coordinating visual information received from the eyes. And to be able to process that quickly while they are flying rapidly. That's in contrast to brain evolution in say rodents, where there's been more development of the cerebral cortex.

Answer 47

highly modified forelimb Elaborate joints Fused hand bones Powerful tendons and compact tiny muscles

Answer 48

The humerus, ulna and radius bones are homologous to those in the limbs of other vertebrates. But they have more elaborate joints which permit the wing readily to change position and angle during takeoff, flight and landing. When outstretched, these joints are strong enough to withstand the wrenching forces created during flight. And that's helped by having fused hand bones, there are only three digits in the birdwing as opposed to the five found in most tetrapods. That fusion provides strength and rigidity in the outer wing skeleton. And then for their support and manoeuvrability for the large primary flight feathers. Within the wing itself are powerful tendons and compact packages of tiny muscles that can control really in a detailed way the wing positions.

Answer 49

Airfoil in cross section- that is it has this rounded leading edge and a sharp trailing edge. An asymmetric profile is fundamental to generating lift crucial for flight.

Answer 50

Bird flight is governed by the laws of physics, just like aeroplane flight. And that means that there are two sets of competing forces at work .

Answer 51

Weight vs lift Drag vs propulsion to counteract the downward force of gravity, which is expressed as a birds weight . an upward air pressure force known as lift must be generated. To counter the slowing influences of the forces of turbulence and friction. Which are collectively known as drag. The forward force called propulsion or thrust must be created. When these four forces are in dynamic balance. A bird maintains a level flight at a constant speed. Unlike aeroplanes which generate lift with wings and thrust with engines. Birds use their wings to do both.

Answer 52

birds have of course evolved to be as light as possible. That's the reason for those lightning adaptations that we saw. Things like having a reduced number of bones, having hollow bones, no teeth, no bones in the tail. And having those reproductive adaptations that all reduce weight and thus the pull of gravity by minimising weight birds minimise the amount of lift that they have to generate. result of gravity reduced as much as possible

Answer 53

Now lift is generated by the flow of air over the wings, to understand how this works we have to understand that there is a relationship between the speed of air flow and the pressure created. This is something known as Bernoulli’s principle. speed of air flow flow relates to pressure. Further to travel, air speeds up, pressure reduced Wing sucked upwards. Shorter distance, air slower, pressure increased, Wing pushed upwards. More curved the airfoil, greater the lift.

Answer 54

Remember that the wing has this airfoil shape, this rounded front edge, this trailing tapering edge and its this airfoil shape that is so important for the generation of lift. Across that top curved surface there is farther for the air to travel. It therefore speeds up and sir that is travelling faster, generates less pressure.this means that the wing is sucked upwards. Simultaneously air passing underneath this airfoil shape has a shorter distance to travel. The air therefore travels slower which creates an increased pressure. That pushes the wing upwards. So we are getting lift because of this asymmetric shape of the wing with different distances for the air to travel across each of the two surfaces. The amount of lift generated increases with airspeed and with the volume of air deflected over the wing. Moreover the orientation or angle of attack of a wing in a current of air also affects the generation of lift. Increasing the angle of attack, basically making the airfoil more curved increases the amount of lift generated . however if that angle of attack becomes too great, stalling occurs. Birds actually do this deliberately when they are coming into land, because then its beneficial to bleed off that lift and consequently their speed too.

Answer 55

Friction | Induced

Answer 56

Consequences of air flow over body Resistance to anything passing through air. Friction drag is the drag produced by the flow of air over a body. And this is influenced by uneven surfaces or anything jutting out. Basically from the body so theres resistance to anything passing through the air. That resistance is greater the more projections there are. That means that reducing drag is aided by streamlining.ome of the advantages of the contour feathers is that they can be locked together to produce this streamlined surface.

Answer 57

the second type of drag is induced drag, this is the consequence of lift so we have air passing at different speeds over the top and the lower surface of the airfoil shaped wing. When those two air flows then meet at the wing tip , what is generated is the swirling wingtip vortices. These swirling vortices generate this induced drag, pulling the bird back, holding it back to some extent. These forces, this induced drag is also dependent on the bird speed. So at increased speed there is increased induced drag at the wing tips. And this induced drag produces a downwash, effectively it pulls the bird back a little bit.

Answer 58

But you can take advantage of the induced drag, the wingtip vortices of others if you fly in the right formation. So this is something we see in terms of long distance migrating birds like geese or cranes where we see them flying in this V formation. And thats bc if you fly just behind and just below the bird in front in a certain position, you can take advantage of those swirling vortices of the bird in front. And that reduces your own energetic cost of flying. Its analogous to the slipstreaming you can do in the cycling race if you get in just behind the bike in the front.

Answer 59

Propulsion/thrust - created when wings flapped - majority of force in powered downstroke - simple recovery upstroke. Final force to consider is this forward momentum, propulsion or thrust. This is created by the flapping of birds wings . the majority of the force in most birds is in the powered downstroke that is generated by the pectoralis muscle. The huge muscle in many bird species. In most species there is a simple recovery upstroke that just gets the wing back into the position for that power downstroke.

Answer 60

most simplified types of flight is gliding and this illustrates how forces of weight, lift and drag can work. Gliding birds are using their weight to overcome air resistance to forward motion. That means that the heavier the bird is the better they tend to be at gliding, so you really only see gliding or certainly gliding for long distances in large heavy birds. Effectively youre always going to be losing height because as you go along without some other reason to generate that. But the amount of height you are losing while gliding also varies in terms of the distance traveled, so how far you can get for the same height lost basically is dependent on the weight of the bird. weight used to overcome air resistance to forward motion Generally used by large birds Height lost/ distance travelled.

Answer 61

So on the left here we have a Fulmar, a seabird weighing about 800g. And in normal conditions it can travel about 8 meters for every 1 metre of height lost while gliding. By contrast the much heavier bald eagle can get about 20 metres for every metre of height lost while it is gliding.

Answer 62

ne way in which height can be gained without going through flapping flight is through soaring.This is maintaining or indeed increasing altitude without flapping. What you need are updrafts of air, which you can then take advantage of and these updrafts can aride in several different scenarios. For instance, there are things called slope soaring. So this is the situation where wind is deflected upwards by the side of objects. Hillside or a mountain side, or even a building. This is the updraft thats often used by human gliders. If you see them along the coastline, making use of these updrafts along the edges of cliffs. Another type of soaring is whats known as dynamic soaring. This is making use of the little localised updrafts when wind meets waves out in the open oceans. So thats just above the surface of the ocean. There are these little updrafts from each individual wave. If you can keep catching those then you can soar for hours at a time with no flapping flight. This is something that the albatrosses are highly adapted to do hours of flying just above the ocean surface with no active flapping flight needed.

Answer 63

Maintain or increase altitude without flapping Slope soaring- wind deflected upwards by side objects Dynamic soaring- local updrafts when wing meets waves.

Answer 64

Thermal soaring: uneven heating of air near ground creates convective currents that cause air to circulate In terms of soaring theres whats known as thermal soaring, this is because there is uneven heating of air near the ground, which creates convection currents, causing air to circulate upwards. So you end up with these columns of circulating warm air. And thats why birds using these thermals tend to fly in circles. They are trying to stay in this column of upward moving air. This is particularly generated in areas of hot climates. And as thermals are generally not developed over large water birds tend to collect in large numbers in places like Gibraltar where they try to obtain as much height as they can on the basis of thermals to then help them negotiate the straits into Africa with minimal active flapping flight, so they are trying to save energy by getting as high as possible in the thermals before crossing the seas. Birds in thermals typically fly in circles

Answer 65

•Adds thrust •Asymmetric wing actions •Steering, turning and twisting controlled by numerous muscles. Flapping flight of course adds thrust this forward momentum to the controlling forces. Each primary feather acts as an airfoil, as does the wing as a whole. And you've got these 50 or so different muscles controlling the wing movements: some fold, others unfold it, some pulling up, some pull it down, and still others adjust its exact orientation, allowing precise steering, turning and twisting during active flight.

Answer 66

Maintaining stationary position in the air. Finally there is hovering, birds can achieve this in two ways. Hovering in general means maintaining a stationary position in the air relative to the ground below you. In some large bird species this is done by wind hovering.

Answer 67

Windhovering- fly into headwind and use thrust to fly slowly. True hovering-wing airfoil shape in up and down stroke

Answer 68

So in this Osprey for example what it does is it flies into a headwind that exactly the pace needed to maintain a position above the surface below. And its doing that because in the case of the Osprey, its looking for fish to feed on. So its trying to hold a stationary position in the air to be able to have a clearview and lookout for its lunch. The real experts, those species that can manage true hovering, so even in still air. well , the largest of those in the world is something called a pied kingfisher in Africa. But the real experts are the hummingbirds. And they achieve this because, unusually they have power in both their downstroke and their upstroke. They can flip their wing over such that theres an airfoil shape both times round. And they can generate perhaps 52 beats per second, which means that not only are they flapping very very fast, but both the upstroke and downstroke generates power.

Answer 69

Wing shapes- vary substantially among species. And the shape of the wing is an important factor in determining the types of flight of which the bird is capable or best adapted. Different shapes correspond to different tradeoffs between beneficial characteristics, such as speed, low energy use, gliding ability, and aerial agility. If we look at the planform of the wing, thats the shape of the wing as seen from below. It can be described in terms of two parameters.

Answer 70

First of the two parameters is known as wing loading- thats the ratio of weight to wing area and it determines the costs of flight. Birds with a low wing loading have a large wing area for a particular body weight. The other extreme we have birds with a high wing loading that is a relatively small wing area for a particular body weight. Birds with low wing loading tend to need less power to sustain flight. And these species tend to fly more slowly and that are more maneuverable than those with higher wing loadings. Low wing loading - Large wing area for a particular body weight. High wing loading - Small wing area for a particular body weight.

Answer 71

Body weight/ wing area

Answer 72

Higher wing loading can also be a problem in terms of taking off. You've got to get this big weight off the ground with a relatively small wing area. For example swans which are taking off from ground level- the only way that they can do this is to run along the surface of the water while flapping, they are trying to generate sufficient speed to get enough lift to get off the ground. Vultures are also species with high wing loadings but they stand on the top of things like cliffs and just launch themselves into space and that downward momentum and that increase in speed as they plummet results in lift sooner rather than later.

Answer 73

The second parameter, in terms of wing shape, is called the aspect ratio. Thats the ratio of the wingspan to the wing area. Generally the higher the aspect ratio that is longer narrower wings , the lower the induced drag produced by the wing at a given speed, remember induced drag is generated at the wing tips due to the different speeds of air passing over the top and bottom surfaces of the airfoil shaped wing. Most bird wings can be grouped into four types of aspect ratio. Of course it's more like a continuum but its easier to categorise in general senses. Particularly when we are interested in thinking about what particular aspect ratios generate in terms of characteristics for flight.

Answer 74

Wing breadth squared/ wing area

Answer 75

high lift wings

Answer 76

These have a moderate aspect ratio. They’re also pretty broad wings, just like the elliptical ones, but somewhat longer. They are also heavily cambered and these wings are particularly good for carrying a heavy load, so a big body mass, whilst minimising the energy needed to fly. These high lift wings are particularly common in terrestrial soaring species. Things like the Eagles, the vultures and the storks. These are the species that are particularly making use of thermal soaring. Remember those columns of circulating warm air rising from the surfaces? And these high lift wings are excellent to allow broad turns, as the birds circle inside these thermals and to catch those thermals and lift the birds to higher and higher altitudes. These high lift wings also suffer from lots of induced drag, so we often see wing slots in these species too. * Moderate aspect ratio * Heavily cambered * Carry heavy load, but minimise energy * Terrestrial soaring species (e.g. eagles, vultures, storks)

Answer 77

* Relatively high aspect ratio * Almost flat profile * Aerial feeding (e.g. swallows, swifts) * Long migrations (e.g. shorebirds) A third type of wing is the high speed wing. This is rather different, these have a relatively high aspect ratio. They have an almost flat profile, but you’ve got this pointed slender wingtip. So theres no need here for any wing slotting because already the level of induced drag in minimised. And they have a swept back look too. These high speed wings are particularly suited to species that feed aerially chasing invertebrate prey up in the sky. So we see high speed wings in, for example, swallows and swifts. These narrow tapering wings can also be flapped rapidly to generate lots of speed with minimal drag. That means they are also good for long migrations, so we see this type of wing shape in many shore birds, which migrate big distances between breeding and wintering grounds.

Answer 78

* High aspect ratio * Narrow, pointed shape reduces drag while gliding * Sea birds in windswept environments (e.g. albatrosses). The final wing shape is this soaring wing shape. They have a very high aspect ratio, that these long thin tapering wings again because of that narrow wingtip, theres no need for wing slotting. And these are particularly good at reducing all sorts of drag whilst gliding. We therefore see these soaring types of wing shape, particularly in seabirds in windswept environments. Classic example being the albatrosses- which are experts at dynamic soaring. Picking up these little updrafts from individual waves out in the open ocean, constantly adjusting and making use of those soaring options close to the ocean surface. And these soaring wing shapes are ideal for that way of life.

Answer 79

Flight is often important for feeding, take these hummingbirds, for e.g. they have to move from flower to flower, be able to extract the nectar constantly, and move on. Others are feeding on invertebrates that they are chasing in the sky. Still others are using flight to be able to spot prey down on the ground before diving down to pounce upon it.

Answer 80

Flight is also sometimes important in courtship. Here we have a male and a female in perfect synchrony during a courtship flight. While they are choosing a partner. And flight opens up travelling for huge distances. There is no way that a mammal of an equivalent size could travel such massive distances as exhibited by this Willow warbler. They weigh only a few grams and yet annually they make a migration from Alaska to Sahara, 10,000 kilometres or so. That is only made possible through flight.

Answer 81

Increased weight Reduced buoyancy Smaller wings There are some species which spend much more time under water like these penguins. In these species there is increased weight compared to those birds that fly in the air, you don’t need to overcome gravity compared to those flying in air, and indeed you might want reduced buoyancy so you don't have this same hollowing out of the bones, for instance. These species flying underwater also have much smaller wings. They don't have to generate lift and thrust in air. Instead they are much more useful for steering underwater.

Answer 82

Expensive No need if reduced predatory risk Not all modern day birds fly, there has secondarily been the loss of flight in some species, like the brown kiwi. The reason for that is that flight is incredibly energetically expensive. Thus if you can get away without needing it, then you can save that energy for other parts of your life. For instance, if you live on an island where there are no terrestrial predators. Then theres no need for flight to escape that threat. In which case there is the possibility to have evolved the loss of flight and saving of all that energetic output.

Answer 83

``` •Adaptations –Feathers, lightening, strengthening, brain and sensory organs, wings •Mechanics –Weight, lift, drag, thrust •Types of flight –Gliding, soaring, flapping, hovering •Wing shapes –Elliptical, high speed, soaring, high lift –Feeding, courtship, migration, diving ```

Answer 84

Elliptical. First wing shape we can think about •Low aspect ratio- their broad chunky wings if you like •Good manoeuvrability (e.g. woodpeckers, forest raptors)- birds with these types of wings have good manoeuvrability, they can flap them very relatively fast. They can manoeuvre well. That means they are extremely useful in tight environments, so when theres lots of vegetation around, in say woodlands or forests. So birds like woodpeckers and forest raptors have these elliptical wing shapes. •Fast take-off (e.g. pheasants, grouse)- this type of wing shape also allows fast takeoff from the ground. Thats especially useful for species that forage predominantly on the ground, but which are vulnerable to terrestrial predators. Think here things like pheasants and grouse, as they move along the ground looking for food. If they spot a fox, they need to get out of the way off the ground quickly, and these elliptical wings are best for that. The trouble with these broad wings with a low aspect ratio is that they generate large amounts of induced drag. •Slotting- Birds with elliptical wing shapes have therefore evolved this, slotting on the wing tips. This is the gaps that you see in the diagram between the feathers. That allows air to pass through and dissipate and the bending of the feathers leads to the displacement of the wingtip vortices. Spreading it over a greater area of the wing and leading to reduced induced drag.