Talk:Bird flight/Archive 1

Archive 1

high aspect ratio wings

This kind of wing is not discusses in the article dispite it being one of the four kinds mentioned before introducing the other threeHerle King 06:31, 18 February 2007 (UTC)

Yeah! And it used to be, when I started the article I included it. I wonder why it was taken out? Sabine's Sunbird talk 07:49, 18 February 2007 (UTC)

It was removed by a vandal. This has now been reverted. Robin S 23:37, 14 August 2007 (UTC)

Adaptations for flight

To deal with the high metabolic demands of flight, birds have also developed a monodirectional pulmonary system, so that air flows in only one direction past the capillaries. --Eric Forste 00:23, 21 Jun 2005 (UTC)

What exactly does this mean? Sorry for my ignorance, I would've changed it otherwise. Does it mean that birds have some kind of unidirectional breathing (i.e. two openings, an air intake and an air outflow). Otherwise, what can it mean? zrenneh 19:05, 20 April 2007 (UTC)

Evolution is not purposeful

Several times in this article we are asked to believe that birds, or their body parts, changed purposefully. Evolution does not work this way. Neither the process of evolution, nor any animal body part, is goal-directed.

- JB Cassel

• It's bad wording on my part rather than intention. I'll try to change what I can find, feel free to change what I miss. Sabine's Sunbird 9 July 2005 19:10 (UTC)

Antioxidant Systems

Can anyone point me in the direction of finding out more about the advanced free radical fighting powers of birds?

From [1] Uric acid (which is mostly formed from purine degradation) protects Vitamin C from oxidation by divalent ions and can act as an anti-oxidant. Uric acid also protects against free-radical catalysis by binding iron. Humans have higher levels of uric acid than monkeys and other mammals because humans lack the enzyme uricase. But birds typically have twice the plasma uric acid concentration as humans. Birds often live several times as long as comparably sized mammals despite over twice the metabolic rate, 2-6 times the plasma glucose and a 3ºC higher body temperature.

Mammals fed anti-oxidants show up to a 30% increase in average lifespan, but no increase in maximum lifespan. Anti-oxidants are most valuable for animals that are cancer-prone, or subjected to radiation or chemical toxins. There are evidently homeostatic mechanisms in cells that govern the amount of allowable anti-oxidant activity. For example, increased levels of Vitamin E in the diet correlates with reduced levels of glutathione peroxidase activity, and vice versa. Vitamin E was shown to increase catalase in banana fruit-flies -- with increasing doses of Vitamin E extending fruit-fly lifespan up to a dose of 5 micrograms/mL, above which increasing doses decreased lifespan [GERONTOLOGY 42:312-321 (1996)]. --Son of Paddy's Ego 00:23, 28 September 2005 (UTC)

Basic mechanics of bird flight

This paragraph was moved to the end so page can be read in sequence

Hi,

The lift section was just wrong. [2].

P.

Hello!! I was just about to say exactly the same, on coming here I realised someone else has pointed this out. Now the question for me is, how much exactly (or aproximately) does Bernoulli effect help birds fly? It's been already pointed out in the Wikipedia article for Wings that aircrafts fly mainly due to the Coanda effect, more or less the same says this excelent page on "http://jef.raskincenter.org/published/coanda_effect.html" - the page you point out mentions "Reaction lift" - I think it would be great to correct/expand the article mentioning this kinds of lift, too.

There are conspiracy theories everywhere from Kennedy's assassination to how a wing works. NASA is not hiding the truth! Occasionally a maverick comes along and challenges orthodoxy, like Wegener, but people who invoke the Coanda effect to explain normal aerodynamic lift are not prophets crying in the wilderness. 99.9% of professional aerodynamicists use the conventional explanation every day and in doing so produce successful aircraft, not by trial and error but with mathematics. (The other 0.1% are just eccentrics.) Unlike conventional aerodynamics, the 'Coanda theory' cannot be used to make further calculations, such as predicting the depth of the boundary layer. This is the ultimate test of any scientific theory, which it fails. The fact that a Wikipedia article states otherwise only proves that the majority do not understand aerodynamics.

There is a real Coanda effect, which has been used to generate lift using a jet blowing over a curved surface. However it needs the flow from high speed jet to produce enhanced lift, and it does it through turbulent mixing that does not occur above a normal wing.

The 'Coanda-ists' claim that the air “sticks” to the surface because of viscosity. This implies that if the viscosity of the fluid changes, the amount of lift an airfoil produces should change in proportion. Experiments show that the amount of lift produced by a real wing is independent of viscosity over a wide range. In fact the real Coanda effect requires turbulence, so it only occurs if the viscosity is sufficiently low.

The air speeds up the air above its upper surface. Coanda assume that the relative air-flow meets the wing at the same velocity as in free air and then follows the curve. This understates the pressure gradients by an order of magnitude.

There is an explanation on NASA's web site

It is sad when people who do not know a subject feel qualified to edit articles in Wikipedia. JMcC 10:33, 29 November 2005 (UTC)

Hello! After reading this guy's explanation on how flight is possible in [3], i kind of understand your nasty mood in your comments here. However, whoever wrote here "I think it would be great to correct/expand the article mentioning this kinds of lift, too." is an inteligent guy who wants to know more. Aerodynamics is a study that started with empiric observations. We should be greatfull for all the Coanda's out there that proposed (or not) the wrong theories! They paved the way to the more robust ones. Nowadays, we use the full blown Navier-Stokes to compute highly complex and non-linear flows. Not yet for practical uses like modelling an aircraft, but we'll get there soon. But to explain here Navier-Stokes is a bit too heavy, so the classic explanations are more suited. It happens though, that these classic explanations must be mentioned first to what conditions they apply. In effect, the bird flight is comparable to that of an aircraft only when the bird is not flapping the wings. When flapping occurs, the airflow around the wings in no longer steady but highly dynamic. Still today, the theory behind the modelling of modern subsonic aicraft uses models for predicting the boundary layer (which is very important to compute the drag, and every count of drag is measured in thousands of dollars or more) which assume a steady flight with a rigid non-flapping body. For years, the same theories that predicted successfully the aerodynamic behavior of an aircraft, failed to explain how come certain species of heavy bees could fly at all. Later on, research on insect wings saw that the flapping of the wings generates vortexes which change dramatically the airflow around the insect's body. You may hear sometimes someone saying that the insect flies on the vortexes he helps create, because these vortexes generate a pressure gradient across the insect's body which adds the lift that was missing out on the previous theories. Flapping flight is also very advantageous. Dynamic stall happens much later than steady stall, so birds can fly at much higher angles-of-attack. Plus, the flapping moves the wings through the air, so the body can actually be stopped. These two great advantages allow insects with a small brain to fly on with their own lives. Bees, when seen at slow motion, look like drunk drivers, bumping to the walls etc... because controlling flight is a heavy task, but if your flight engine will keep you up in the air no matter what you do, then even bees can do it :)

cheer up dude, the wikipedia is for everyone. The guys who built it believe on the law of the big numbers, i.e. if a lot of people edit this page, the contents will tend to the presently credited as correct version, no matter how many potential idiots change it.

Joao, 11 November 2006

This is a good link for an explanation of wing flight, although it is mostly about insects. http://www.zoo.cam.ac.uk/zoostaff/ellington/aerodynamics.html The diagram Lift-force-en.svg‎ needs a bit of attention and maybe a caption to explain it. attack in Angle of Attack has 2 't's. What is the meaning / interpretation of the Thrust vector? I would have expected thrust to be in the direction of motion (of the bird, not the air) and certainly not in some apparently arbitrary direction. The 'Move direction' seems to be airflow direction. Doesn't it vary with upstroke and downstroke. Do we even know what happens to lift and drag in the up/downstroke?

"During the down-stroke the angle of attack is increased, and is decreased during the up-stroke.[citation needed]" Is this correct? I have found it hard to find a simple explanation, but my impression has been that angle of attack must DECREASE on the down-stroke, since the 'apparent wind' is coming up from below the line of flight and it must INCREASE during the up-stroke as the 'apparent wind' is moving downwards relative to the line of flight. This is consistent with aerodynamic lift on both upstroke and downstroke (in some species). Another good source with a good review is Bret Tobalske -Biomechanics of Bird Flight - http://jeb.biologists.org/cgi/content/full/210/18/3135. There is also no mention of wing shape change by wrist movement which causes wing folding. Sorry - I'm not expert enough to really contribute, but I hope the comments help. (QuietJohn (talk) 06:33, 2 January 2010 (UTC))

Evolution of flight

From what I remember of my ornithology course several years back, ornithologists are still split on what triggered the evolution of flight. IIRC, the "top down" theory (gliding from trees) was postulated first, and the "ground up" theory (running/hopping after insects) was postulated as an alternative, but both have glaring problems. Kenneth Dial has suggested that rudimentary flappnig wings would have been an effective method to run up inclined surfaces.

Does anyone have any objections to a more complete write-up of this section? Ladlergo 16:58, 11 April 2006 (UTC)

Planform is not the same as aspect ratio

The article says, Elliptical wings are short and rounded, having a low aspect ratio. I don't understand this. There's no particular correlation between an eliptical shape and a high or low aspect ratio. You could have high aspect eliptical wings. I'm not sure what the original author was getting at here, so I'm not sure how to correct it. -- RoySmith (talk) 22:38, 11 December 2006 (UTC)

Minor Quibble -- Airspeed Vs Groundspeed

Shouldn't airspeed in:

"Take-off and landing" penultimate sentance: "If timed correctly, the airspeed once the target is reached is virtually nil. "

Be "groundspeed" instead?

DavesTA 23:10, 11 December 2006 (UTC)

Hovering - kestrels

Greetings All, Would be grateful if anyone out there could explain (and include in the article) just how it is that what I took to be a kestrel hovering just a short distance from me the other day was able to stay in one place for several minutes at a time in a very strong head wind without (I am totally sure of this) moving its wings once. In other words, the basic mechanics of flight are perfectly clear, but as I say, I am completely sure that it did not flap its wings to fly slowly into the wind, nor fast like a hummingbird. Can only assume it was some amazing combination of wing/feather positions acting in perfect harmony with the air current. Thanx. --Technopat 21:10, 25 April 2007 (UTC)

Image "African Hawk-Eagle in flight"

This should actually be "African Hawk-Eagle in hand" because this bird is quite obviously being held—look at the angle of the legs. If it was in flight, the photographer would surely have had to be a prey item! :) Not that it's a bad image, but we might want to reword the caption... MeegsC | Talk 00:17, 15 August 2007 (UTC)

Image for "evolution" section

I suggest the image in the taxobox of Archaeopteryx would be more relevant. Philcha (talk) 19:13, 2 April 2008 (UTC)

Bank jumping theory

Protoart added this section, referenced only to a blogsite; that would lead me to believe it has no backing in the scientific community. If that's not the case, a reliable source should be used to justify its reinclusion in the article.

This theory proposes that small bipedal dinosaurs (theropods) were living a semi-aquatic life along rivers, lakes and swamps. They were warm-blooded and had feathers that were used for warmth, sunshade, brooding eggs and for buoyancy to aid in swimming. They waded, foraged or stalked prey in shallow water. They would run and jump feet first to take fish, amphibians, reptiles, etc. Their warm bloodedness would allow them to attack at dawn. They would use their hind leg claws to seize and immobilize prey and their teeth to tear them apart to feed to their young. Later, they jumped from rocks, banks and cliffs head first to capture small fish with their mouths directly. They would use their forelimbs to swim back to shore. Most could succeed from the low rocks. Less would succeed from the high overhangs. Those that succeeded had feathered tufted tails that would be used to stay straight, or within a cone of movement, produce some yaw or pitch to better target moving fish.

A favored race would separate and begin to utilize their feathered forelimbs for attitude control. Their forelimbs and tails would change to aerodynamic fins with the emergence of flight feathers. Quicker pitch and roll and eventually lift will allow them to extend their range. Flapping their forelimbs fins would extend their glide slope. They could dive in head first, belly in or bring their feet forward to seize prey. As they came close to flat water they could utilize the air-cushion affect to glide level. Eventually a fully articulating tail and asymmetrical feathers would allow them to glide up, down or over the river. Integrated anatomical changes will allow them to flap and lift upward to exploit the terrain and greatly extend their hunting range. They would glide up and down river valleys using ridge lift to explore new areas. This mobility would greatly enhance their survival. They could nest far from where they hunted, and they could move seasonally.

This theory explains the first exaptation, the tail, from balance while standing, running and turning, to an aerodynamic steering device. This theory has no risky trial and error scenarios where failure is dangerous, and natural selection would reject. This theory doesn’t need to explain how bipedal animals climbed trees. This theory does not depend on incipient flight feathers without explaining how they came about. This theory doesn't need to ignore that four legged running would serve attack or defense much more effectively than feeble forelimb flapping assist. This theory's initial aerodynamic act, diving for fish, is still performed by some modern birds today.

Bat Flight

I think we should create an article about bat flight. This is why I think we should create an article about bat flight.

• Bats are more agile and maneuverable fliers
• Smaller species of bats can hover like hummingbirds
• Their skin membranes that they use for flight is a lot lighter than a birds set of feathers
• Bat create multiple vortices instead of one like birds, thus their flight is more energy efficient
• Because bats are such agile creatures they can make 180 degree turns on a dime

Here are some links

• [4]
• [5]

—Preceding unsigned comment added by 71.7.88.127 (talk) 21:55, 6 November 2008

Go for it! I don't know that you'll get a huge response from editors here, since most of us are working primarily on bird articles. You might pitch your idea to the folks at WP:MAMMAL though! MeegsC | Talk 19:53, 19 October 2008 (UTC)

Proposed project of interest - organismal biomechanics

Hi all, I'm trying to start a Wikiproject to cover Organismal Biomechanics, and I was wondering if anyone else would be interested? Articles such as animal locomotion. gait, muscle, and similar would be our targets. See my userpage for a list of what I'm planning to work on, including some truly awful articles in desperate need of attention. See proposal page at Wikipedia:WikiProject_Council/Proposals#Wikiproject_Organismal_Biomechanics. I'll keep anyone who signs up updated via their userpages until I get a project page made. Help of all kinds is appreciated, from brain dumps to wikifying, grammar and dealing with references. Mokele (talk) 01:37, 12 March 2009 (UTC)