|[Note Guidelines] Photographer's Note|
|Here's another shot of Kaln the Eagle Owl from the Barn Owl Centre in Gloucester.|
I hope you like it!
The fact that birds fly is one of the most amazing things about them. The sight of crows or ravens playing in the wind, of seagulls gliding effortlessly along seashore or of buzzards soaring silently about the countryside always inspires me.
There is no doubt that if I had the ability to change into another animal, something other than a human being I would be a bird simply because of the incredible wonder of flight on a sunny day.
Birds are the ultimate flying machines, though insects have been doing it for longer and in many cases are more versatile; their small size makes the physics of it much easier. Birds fly far better than any machinery mankind has yet made and like our machines they use their wings and tails in a variety of ways to achieve their expertise.
Bird flight is dependent on the shape of the birds wings and the way they use them. Generally, bird flight can be divided into two modes of functioning, i.e. gliding or soaring flight, and flapping or powered flight.
The dynamics of bird flight like all physical actions are governed by the laws of physics. In its simplest expression, flying is a balance between two sets of forces. lift and weight, and thrust and drag. Weight is the result of gravity and is reduced as much as possible in birds (see anatomy). Lift is generated by the flow of air over the wings.
The red line is the leading edge, the air first hits the wing here. It travels up over the green line and then down the back of the wing where it leaves the wing at the blue line, the trailing edge.
Basically, birds wings are not flat but are shaped like an aerofoil - concave. Air passes over or under the wing as the bird moves forward, or as the wind blows. The air that moves over the top of the wing has further to travel to get across the wing, thus it speeds up. This causes the pressure to drop because the same amount of air is exerting its pressure over a greater area. Therefore, any given point experiences less pressure. This effectively sucks the wing up. Meanwhile the air going below the wing experiences the opposite effect. It slows down, generates more pressure and effectively pushes the wing up. Hence a bird with air moving over its wings is pulled up from above and pushed up from below. The more curved the aerofoil the greater the lift providing the degree of curve does not impede the flow of air.
This is not the end of the story though, because the air passing over the wings and the rest of the body creates drag. This is the resistance the air gives to anything passing through it. The faster you move the more drag you experience because you come into contact with more air per second (or other unit of time). Thirdly, because nature does tend to even things out, the low pressure air on top of the wings represents a sink that the high pressure air under the wing seeks to move towards, a bit like water running down hill. This happens most along the thin trailing edges of the wing and causes a spiralling vortex of disturbance at the wing tip. These spiralling vortices increase drag, therefore, the most efficient wings are those which supply lift while reducing drag. In practice this means the crescent shaped wings of swallows and swifts.
However, birds use flight in different ways, some are on the wing most of the time, while others make only short flights from one perch to another. Also birds live in different habitats which generate different aerodynamic problems. It is not surprising then that birds of different species have different shaped wings.
Changing the shape of a wing gives it different aerodynamic properties. One way to assess these properties is to measure what is called the 'aspect ratio'. This is the ratio of wing area2 divided by wing breadth. Long wings are better for gliding but harder to flap quickly and are therefore not much good at quick acceleration. Another way is to look at flight capabilities is to look at 'Wing Loading', this can show the differences between birds with similar wing shapes but different sizes. Wing loading is the relationship between total body mass and total wing area, it is expressed as grams of body mass over centimetres squared of wing area. Thus the Long-tailed Hornbill (Tockus albocristatus) which weighs 297gram, has an aspect ratio of 4.65 and a wing loading of only 0.175 has light buoyant flight while the Yellow-casqued Wattled Hornbill (Ceratogymna elata) which weighs 2100grams, has an aspect ratio of 4.53 but a wing loading of 0.709 has much heavier and more laboured flight.
Four different basic wing shapes include:
1) Resident passerine or pheasant - wings like this have a low aspect ratio of around 3.0 to 6.0 and allow their owners to explode into flight suddenly and are quite adequate for relatively slow powered flight, but not good for gliding;
2) Waders have medium length wings with an aspect ratio of around 12.5, they also tend to be pointed and directed backwards after the first half. These wings are shower to take off, but allow for a faster top speed and a little gliding. They are good for long distance migrants;
3) Eagles and Vultures have broad, long wings with an aspect ratio of around 9.3 and the feathers at the ends separate out into fingers which help with minute controls (like aerofoils) while the birds are gliding. These are basically terrestrial birds riding high above the ground using a variety of updrafts to avoid flapping;
4) Albatrosses have long, thin wings with an aspect ratio of around 13.8 and higher and no fingers. These are good for gliding over the sea, close to the surface, using small changes in wind direction to maximum advantage. These four examples pinpoint the extremes and among the 9703 species of known birds, wings with many similarities but numerous small variations can be found.
Non-flapping Flight or Gliding
Many soaring or gliding birds appear to hang in the air effortlessly, gaining height with barely a twitch of a wing. These are birds like Vultures, large raptors, Pelicans and Storks with a high lift to drag ratio. Essentially this means that their wings generate a lot of lift without producing much drag. Large birds have evolved to be gliders partly because gliding becomes easier the larger your wings are and obviously small birds cannot have large wings. Secondly, the mechanics of flapping flight become harder to attain the larger you get. This is all related to the fact that mass increases far faster than length. A bird twice as long as another is on average 4 times as heavy. There are other physical constraints to do with the musculature needed to actually flap the wings and the strength needed in the bones to withstand the stresses that these muscles generate. Remember, 'for every action there is an equal and opposite reaction'. Understanding physics is important in biology, however, if all this is a bit complicated just remember that big birds with big wings make better gliders than small birds with small wings.
As an example, Fulmars are excellent flyers. I always enjoy them as they soar around the sea cliffs of Devon. They are excellent gliders and can ride right up to their nests on their stiff unmoving wings. However, Vultures are much much better. A Fulmar in still air can glide quite efficiently, losing only 1 metre in height for every 8.5 metres it travels. The American Black Vulture, however, can glide 22 metres for the loss of only 1 metre in height. This means that an American Black Vulture 501 metres up in the air can, if the air is still, glide 1.1 kilometres or 2/3 of a mile before he hits the ground.
The air is seldom still however and wind changes everything, facing in to the wind you get lift without doing anything but go nowhere while travelling with the wind you get fast forward movement but loss of lift. Physical obstructions like cliffs, mountains and large buildings all cause disturbances in air movement, including updrafts of air. Over some lands the air is heated by reflection and radiation from the sun-heated earth. This produces the thermal updrafts that many of the large birds mentioned earlier use to keep themselves aloft.
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.
Flapping flight is a more complicated process. The bird's wing changes shape during both the up and down stroke. It also changes its angle of attack depending on how much it presses down and how much it pushes backwards. Flapping flight is basically rowing in the air with the added complication that it needs to generate lift as well. If a Blue Tit stops flapping its wings it better be about to land on a branch or it will fall to the ground.
Wing loading is another important way of assessing how and how well a bird flies. Wing loading is the ratio of wing area to weight.
LordPotty, CENT-TRETZE, janhendrik, eqshannon, boreocypriensis, anel, maurydv, jconceicao, rcrick, KOMSIS, siggi, Luis52 has marked this note useful
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|To LordPotty: Book||joey
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- [2009-06-17 1:04]
A great inflight capture,I like the way you composed/cropped the image,good colors and detail especially the bright orange eyes,well done and thanks
Another fantastic Eagle Owl shot,and a very interesting,if rather lengthy,note about bird flight.
Very nice work as usual.
Any sign of that book yet?
Hey Joey, my friend:
How long if your picture comment, I am very sorry I have no excuses to justify it. As you will see little in public and this site is that I'm casting too many places at once. Forgive me.
The picture you present of this bird is beautiful and well-edited because of the difficulty that must capture these moving images. Do you know very well. The written document that includes such a plea is also welcome.
Joey a hug
Ciao Joe, superb capture of wonderful owl in great fly, fantastic red eyes, good details and splendid sharpness, very well done, ciao Silvio
- [2009-06-17 4:47]
Another very beautiful photo of this owl in flight. Great timing. Beautiful natural colours and very sharp. Good POV and composition.
- [2009-06-17 5:14]
Perfect capture, all I can say is Excellent!
Great in-flight shot, pity about the light, but you got the shot none-the-less. Well done.
In this partiuclar one of teh series, I can see plainly or at leas takes up more space, the wing/body feathered area which is so well centered and focused. This looks to me as if it is a bird on a mission. very intense!
- [2009-06-17 11:57]
Hi my young friend! This is a very professional pic,i don't know when i will make a work like that...ehehe....impressive sharpness and colors,the details of the eyes are impressive!!! My best compliments,have a nice day,LUCIANO
- [2009-06-17 13:28]
Hi Joe !
Splendid capture, built and presented exceptional.
Very interesting and description provided by you.
Have a nice evening,
- sotos (313)
- [2009-06-17 14:36]
very nice shot and sharpnes
the eyes isfantastic
Hi and Good Morning mate OwlMan Joey:)
A stunningly perfect in-flight capture of this day-flying Owl from a fine POV with great details and nice composition.
TFS and have a nice day MF!
great shot joe, you have matered this genre of photography too and that too in no time. a fine birder in a youngman , excellent freezing of this moment with good focus,
tfs & regards
- [2009-06-18 4:22]
An excellent shot of this flying Eagle Owl. I like the vertical framing you have chosen. Beautiful too the fine colors of the background. Excellent sharpness on the body of the bird, the wings being a little bit oof, suggest the movement. Interesting note too.Really well done.
another superb picture of the Eagle Owl in flight, outstanding sharpness and splendid colours, POV and composition are excellent.
Light,colours,focus and definition are splendid.
- [2009-06-18 15:40]
Like this one to for all the same reasons, just superb mate.
All the best, Cheers Rick :)
Glad you're back.
an very good pic, pov and sharpness.
With your age you can be later an very good and famous photographer are.
- [2009-06-18 22:06]
Both your in-flights of the Eagle Owl are technically excellent and well timed. Superb lighting and BG. That Sigma 300 f2.8 is a real top quality lens.
Your note is great, well written and with masses of information. If you haven't already done it it would be fine essay on the subject in school. It's pleasant relief from Wikipedia copies.
Thanks mate and have a great Midsummer Weekend, something we celabrate here in Sweden.
- [2009-06-19 10:58]
Kit to the target is ...
Is very good exposure.
Depth of field, excellent details and colors are great owl.
- [2009-06-19 12:07]
a fantastic shot from the owl ,great action shot good sharpnes details colours bg and fantastic yellow eyes .Best regards Siggi
- [2009-06-20 19:11]
Nice to see You are back My young friend, this make me happy and I am sure will
enjoy looking at Your photos and reading excellent notes like this one. WINGS. You see I love birds most of all. You did an excellent and fine work here.