Diferencia entre revisiones de «Visión de las aves»

De Wikipedia, la enciclopedia libre
Ir a siguiente diferencia →
Contenido eliminado Contenido añadido
VisualWikitexto
Rajoch (discusión · contribs.)
1725 ediciones
Traduciendo de la versión inglesa Bird vision
(Sin diferencias)

Revisión del 21:04 18 abr 2009

Uno o varios wikipedistas están trabajando actualmente en este artículo o sección. Es posible que a causa de ello haya lagunas de contenido o deficiencias de formato.
Si quieres, puedes ayudar y editar, pero antes de realizar correcciones mayores contáctalos en sus páginas de discusión o en la del artículo para poder coordinar la redacción.
Uso de esta plantilla: {{En desarrollo|nombre de usuario|t={{sust:CURRENTTIMESTAMP}}}} o {{sust:En desarrollo}}
Con ojos orientados hacia adelante el Pigargo Americano o Águila Calva tiene un amplio campo de visión binocular.

La visión es el más importante de los sentidos de las aves, dado que es esencial para un vuelo seguro, y este grupo tiene un número de adaptaciones que permiten una agudeza visual superior a la de otros grupos de vertebrados. Para resaltar esto, por ejemplo, se ha descrito a la paloma como "dos ojos con alas".[1]​ El ojo de las aves se parece al de los reptiles actuales, pero tiene un mejor posicionamiento de los lentes, una característica compartida con los mamíferos. Las aves tienen los ojos más grandes en relación al tamaño corporal entre todo el reino animal, y el movimiento dentro de la cavidad ósea ocular es limitado por esa causa.[1]​ Adicionalmente a los dos párpados que siempre se encuentran en otros vertebrados, el ojo es protegido por una tercera membrana, móvil y transparente. La anatomía interna del ojo es similar a la de otros vertebrados, pero tiene una estructura, el pecten, única de las aves.

Las aves , como los peces, anfibio y reptiles, tienen cuatro tipos de receptores de color en el ojo. La mayoría de los mamíferos tienen dos tipos, aunque los primates tienen tres. Esto les da a las aves la habilidad de percibir no solo la luz en el espectro visible, sino también en el ultravioleta, y otras adaptaciones permiten la detección de luz polarizada. Las aves tienen proporcionalmente más receptores de luz en la retina que los mamíferos, y más conecciones nerviosas entre los fotorreceptores y el cerebro.

Algunos grupos de aves tienen modificaciones específicas para su sistema visual ligadas a sus modos de vida. Las aves de presa tienen una alta densidad de receptores y otras adaptaciones para maximizar la agudeza visual. La posición de sus ojos les dan buena visión binocular permitiendoles una adecuada apreciación de las distancias. Las especies nocturnas tienen ojos tubulares, con poco numero de detectores de color, pero una alta densidad de células bastoncillos los que detectan mejor la luz menos intensa. Los charranes, gaviotas y albatros están entre las aves marinas que tienen gotas de aceite rojas y amarillas en los receptores de color para mejorar la visión a distancia, especialmente en condiciones brumosas.

Anatomía extraocular

El parecido mayor del ojo de un ave es con el de los reptiles. A diferencia del ojo de mamíferos, no es esférico, y la forma aplanada permite que sea enfocado un mayor campo visual. Un círculo de placas óseas, el anillo esclerótico, rodea el ojo y lo mantiene rígido, pero una mejora sobre el ojo de los reptiles, que también se encuentra en mamíferos, es que el lente es empujado más hacia adelante, incrementando el tamaño de la imagen en la retina.[2]​

Campos visuales de un búho y de una paloma.

Most birds cannot move their eyes, although there are exceptions, such as the Great Cormorant.[3]​ Birds with eyes on the sides of their heads have a wide visual field, useful for detecting predators, while those with eyes on the front of their heads, such as owls, have binocular vision and can estimate distances when hunting.[4]​ The American Woodcock probably has the largest visual field of any bird, 360o in the horizontal plane, and 180o in the vertical plane.[5]​

The eyelids of a bird are not used in blinking. Instead the eye is lubricated by the nictitating membrane, a third concealed eyelid that sweeps horizontally across the eye like a windscreen wiper.[6]​ The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds when they are under water.[7]​ When sleeping the lower eyelid rises to cover the eye in most birds, with the exception of the horned owls where the upper eyelid is mobile.[8]​

La membrana nictitante de una gallina.

The eye is also cleaned by tear secretions from the lachrymal gland and protected by an oily substance from the Harderian glands which coats the cornea and prevents dryness. The eye of a bird is larger compared to the size of the animal than for any other group of animals, although much of it is concealed in its skull. The Ostrich has the largest eye of any land vertebrate, with an axial length of 50 mm (2 in), twice that of the human eye.[1]​

Bird eye size is broadly related to body mass. A study of five orders (parrots, pigeons, petrels, raptors and owls) showed that eye mass is proportional to body mass, but as expected from their habits and visual ecology, raptors and owls have relatively large eyes for their body mass.[9]​

Behavioural studies show that many avian species focus on distant objects preferentially with their lateral and monocular field of vision, and birds will orient themselves sideways to maximise visual resolution. For a pigeon, resolution is twice as good with sideways monocular vision than forward binocular vision, whereas for humans the converse is true.[1]​

El Petirrojo Europeo tiene ojos relativamente grandes, y comienza a cantar temprano en la mañana.

The performance of the eye in low light levels depends on the distance between the lens and the retina, and small birds are effectively forced to be diurnal because their eyes are not large enough to give adequate night vision. Although many species migrate at night, they often collide with even brightly lit objects like lighthouses or oil platforms. Birds of prey are diurnal because, although their eyes are large, they are optimised to give maximum spatial resolution rather than light gathering, so they also do not function well in poor light.[10]​ Many birds have an asymmetry in the eye's structure which enables them to keep the horizon and a significant part of the ground in focus simultaneously. The cost of this adaptation is that they have myopia in the lower part of their field of view.[1]​

Birds with relatively large eyes compared to their body mass, such as Common Redstarts and European Robins sing earlier at dawn than birds of the same size and smaller body mass. However, if birds have the same eye size but different body masses, the larger species sings later than the smaller. This may be because the smaller bird has to start the day earlier because of weight loss overnight.[11]​

Nocturnal birds have eyes optimised for visual sensitivity, with large corneas relative to the eye’s length, whereas diurnal birds have longer eyes relative to the corneal diameter to give greater visual acuity. Information about the activities of extinct species can be deduced from measurements of the sclerotic ring and orbit depth. For the latter measurement to be made, the fossil must have retained its three-dimensional shape, so activity pattern cannot be determined with confidence from flattened specimens like Archaeopteryx, which has a complete sclerotic ring but no orbit depth measurement.[12]​

Anatomía del ojo

Anatomía del ojo de ave.

The main structures of the bird eye are similar to those of other vertebrates. The outer layer of the eye consists of the transparent cornea at the front, and two layers of scleraPlantilla:Ndash a tough white collagen fibre layer which surrounds the rest of the eye and supports and protects the eye as a whole. The eye is divided internally by the lens into two main segments: the anterior segment and the posterior segment. The anterior chamber is filled with a watery fluid called the aqueous humour, and the posterior chamber contains the vitreous humour, a clear jelly-like substance.

The lens is a transparent convex or 'lens' shaped body with a harder outer layer and a softer inner layer. It focuses the light on the retina. Its shape can be altered by means of the ciliary muscles which are attached to the eye by means of the zonular fibres. In addition to these muscles, some birds also have a second set, Crampton’s muscles, that can change the shape of the cornea, thus giving birds a greater range of accommodation than is possible for mammals. The iris is a coloured muscularly operated diaphragm in front of the lens which controls the amount of light entering the eye. At the centre of the iris is the pupil, the variable circular area through which the light passes into the eye.[2]​

Los colibríes están entre las aves con dos foveas.

The retina is a relatively smooth curved multi-layered structure containing the photosensitive rod and cone cells with the associated neurons and blood vessels. The the density of the photoreceptors is critical in determining the maximum attainable visual acuity. Humans have about 200,000 receptors per mm2, but the Gorrión Doméstico has 400,000 and the Busardo Ratonero 1,000,000. The photoreceptors are not all individually connected to the optic nerve, and the ratio of nerve ganglia to receptors is important in determining resolution. This is very high for birds; the White Wagtail has 100,000 ganglion cells to 120,000 photoreceptors.[2]​

Rods are more sensitive to light, but give no colour information, whereas the less sensitive cones enable colour vision. In diurnal birds, 80% of the receptors may be cones (90% in some vencejos) whereas nocturnal owls have almost all rods. As with other vertebrates except placental mammals, some of the cones may be double structures. These can amount to 50% of all cones in some species.[13]​

Towards the centre of the retina is the fovea which has a greater density of receptors and is the area of greatest forward visual acuity, i.e. sharpest, clearest detection of objects. In 54% of birds, including aves de presa, martín-pescadores, colibríes y golondrinas, there is second fovea for enhanced sideways viewing. The optic nerve is a bundle of nerve fibres which carry messages from the eye to the relevant parts of the brain and vice-versa. Like mammals, birds have a small blind spot without photoreceptors at the optic disc, under which the optic nerve and blood vessels join the eye.[2]​

The pecten is a poorly understood body consisting of folded tissue which projects from the retina. It is well supplied with blood vessels and appears to keep the retina supplied with nutrients,[1]​ and may also shade the retina from dazzling light or aid in detecting moving objects.[2]​

The choroid is a layer situated behind the retina which contains many small arteries and veins. These provide arterial blood to the retina and drain venous blood. The choroid contains melanin, a pigment which gives the inner eye its dark colour, helping to prevent disruptive reflections.

Percepción de la luz

Los cuatro pigmentos en los Célula conoconos de las aves extienden el espectro de visión de color hasta el ultravioleta.[14]​[15]​.


The four pigments in a bird's cones extend the range of colour vision into the ultraviolet[14]​[15]​]] There are two sorts of light receptors in a bird’s eye, rods and cones. Rods, which contain the visual pigment rhodopsin are better for night vision because they are sensitive to small quantities of light. Cones detect specific colours (or wavelengths) of light, so they are more important to colour-oriented animals such as birds.[16]​ Most birds are tetrachromatic, possessing ultraviolet (UV) sensitive cone cells in the eye as well as those for red, green and blue,[17]​ but pigeons have an additional pigment and are therefore pentachromic.[18]​

The four spectrally distinct cone pigments are derived from the protein opsin, linked to a small molecule called retinal, which is closely related to vitamin A. When the pigment absorbs light the retinal changes shape and alters the membrane potential of the cone cell affecting neurones in the ganglia layer of the retina. Each neurone in the ganglion layer may processes information from a number of photoreceptor cells, and may in turn may trigger an nerve impulse to relay information along the optic nerve for further processing in specialised visual centres in the brain. The more intense a light, the more photons are absorbed by the visual pigments, the greater the excitation of each cone, and the brighter the light appears.[16]​

Diagrama de un célula cono de ave.

By far the most abundant cone pigment in every bird species examined is the long-wavelength form of iodopsin, which absorbs at wavelengths near 570 nm. This is roughly the spectral region occupied by the red- and green-sensitive pigments in the primate retina, and this visual pigment dominates the colour sensitivity of birds.[18]​ In penguins, this pigment appears to have shifted its absorption peak to 543 nm, presumably an adaptation to a blue aquatic environment.[19]​

The information conveyed by a single cone is limited: by itself, the cell cannot tell the brain which wavelength of light caused its excitation. A visual pigment may absorb two wavelengths equally, but even though their photons contain different energies, the cone cannot tell them apart, because they both cause the retinal to change shape and thus trigger the same impulse. For the brain to see colour, it must compare the responses of two or more classes of cones containing different visual pigments, so the four pigments in birds give increased discrimination.[16]​

Each cone of a bird or reptile contains a coloured oil droplet; these no longer exist in mammals. The droplets, which contain high concentrations of carotenoids, are placed so that light passes through before reaching the visual pigment. They act as filters, removing some wavelengths and narrowing the absorption spectra of the pigments. This reduces the response overlap between pigments and increases the number of colours that a bird can discern.[16]​ Six types of cone oil droplets have been identified; five of these have carotenoid mixtures that absorb at different wavelengths and intensities, and the sixth type has no pigments.[20]​

The colours and distributions of retinal oil droplets vary considerably among species, and is more dependent on the ecological niche utilised (hunter, fisher, herbivore) than genetic relationships. As examples, diurnal hunters like the Golondrina Común and birds of prey have few coloured droplets, whereas the surface fishing Charrán Común has a large number of red and yellow droplets in the dorsal retina. The evidence suggests that oil droplets respond to natural selection faster than the cone's visual pigments.[18]​

Migratory songbirds use the Earth’s magnetic field, stars, the Sun, and polarised light patterns to determine their migratory direction. An American study showed that migratory Gorrión sabanero comúns used polarised light from an area of sky near the horizon to recalibrate their magnetic navigation system at both sunrise and sunset. This suggested that skylight polarisation patterns are the primary calibration reference for all migratory songbirds.[21]​ However, it appears that birds may be responding to secondary indicators of the angle of polarisation, and may not be actually capable of directly detecting polarisation direction in the absence of these cues.[22]​

Ultravioleta

El Cernícalo Vulgar puede detectar los rastros de orina que reflejan el ultravioleta dejados por sus presas los campañoles.

Birds can perceive ultraviolet light, which is involved in courtship. Many birds show plumage patterns in ultraviolet that are invisible to the human eye; some birds whose sexes appear similar to the naked eye are distinguished by the presence of ultraviolet reflective patches on their feathers. Male herrerillos europeos have an ultraviolet reflective crown patch which is displayed in courtship by posturing and raising of their nape feathers.[23]​ Male Azulejón o Picogrueso Azuls with the most, brightest and most UV-shifted blue in their plumage are larger, hold the most extensive territories with abundant prey, and feed their offspring more frequently than other males do.[16]​

The bill’s appearance is important in the interactions of the Mirlo Común. Although the UV component seems unimportant in interactions between territory-holding male, where the degree of orange is the main factor, the female responds more strongly to males with bills with good UV-reflectiveness.[24]​

A UV receptor may give an animal an advantage in foraging for food. The waxy surfaces of many fruits and berries reflect UV light that might advertise their presence.[16]​ cernícalos vulgares are able to locate the trails of voles visually. These small rodents lay scent trails of urine and faeces that reflect UV light, making them visible to the kestrels, particularly in the spring before the scent marks are covered by vegetation.[25]​

Percepción del movimiento

Un Cernícalo Vulgar necesita para cazar una imagen visual segura.

Birds can resolve rapid movements better than humans, for whom flickering at a rate greater than 50 Hz appears as continuous movement. Humans cannot therefore distinguish individual flashes of a fluorescent light bulb oscillating at 60Hz, but periquitos comúnes and chickens have flicker thresholds of more than 100 Hz. A Gavilán de Cooper can pursue agile prey through woodland and avoid branches and other objects at high speed; to humans such a chase would appear as a blur.[5]​

Birds can also detect slow moving objects. The movement of the sun and the constellations across the sky is imperceptible to humans, but detected by birds. The ability to detect these movements allows migrating birds to properly orient themselves.[5]​

To obtain steady images while flying or when perched on a swaying branch, birds hold the head as steady as possible with compensating reflexes. Maintaining a steady image is especially relevant for birds of prey.[5]​

Percepción de campos magnéticos

The perception of magnetic fields by migratory birds has been suggested to be light dependent.[26]​ Birds move their head to detect the orientation of the magnetic field.[27]​ Studies on the neural pathways have suggested that birds may be able to "see" magnetic fields.[28]​

Aves de presa diurnas

Ojo de un halcón, "vista de águila" es una expresión para describir agudeza visual.

The visual ability of birds of prey is legendary, and the keenness of their eyesight is due to a variety of factors. Raptors have large eyes for their size, 1.4 times greater than the average for birds of the same weight,[9]​ and the eye is tube-shaped to produce a larger retinal image. The retina has a large number of receptors per square millimetre, which determines the degree of visual acuity. The more receptors an animal has, the higher its ability to distinguish individual objects at a distance, especially when, as in raptors, each receptor is typically attached to a single ganglion.[1]​

Many raptors have foveas with far more rods and cones than the human fovea (65,000 mm2 in Cernícalo Americano, 38,000 in humans) and this provides these birds with spectacular long distance vision. The fovea itself can also be lens-shaped, increasing the effective density of receptors further. This combination of factors gives Buteo busardos distance vision 6 to 8 times better than humans.

Cada retina del Águila Mora tiene dos foveas.[29]​

The forward facing eyes of a bird of prey give binocular vision, which is assisted by a double fovea.[2]​ The raptor's adaptations for optimum visual resolution (an Cernícalo Americano can see a 2–mm insect from the top of an 18–m tree) has a disadvantage in that its vision is poor in low light level, and it must roost at night.[1]​ Raptors may have to pursue mobile prey in the lower part of their visual field, and therefore do not have the lower field myopia adaptation demonstrated by many other birds.[1]​ Scavenging birds like buitres do not need such sharp vision, so a cóndor has only a single fovea with about 35,000 receptors mm2

Raptors lack coloured oil drops in the cones, and probably have similar colour perception to humans, and lack the ability to detect polarised light. The generally brown, grey and white plumage of this group, and the absence of colour displays in courtship suggests that colour is relatively unimportant to these birds.[2]​

In most raptors a prominent eye ridge and its feathers extends above and in front of the eye. This "eyebrow" gives birds of prey their distinctive stare. The ridge physically protects the eye from wind, dust, and debris and shields it from excessive glare. The Águila Pescadora lacks this ridge, although the arrangement of the feathers above its eyes serves a similar function; it also possesses dark feathers in front of the eye which probably serve to reduce the glare from the water surface when the bird is hunting for its staple diet of fish.[5]​

Aves nocturnas

Búho Real.

Los búhos have very large eyes for their size, 2.2 times greater than the average for birds of the same weight,[9]​ and positioned at the front of the head. The eyes have a field overlap of 50–70%, giving better binocular vision than for diurnal birds of prey (overlap 30–50%).[30]​ The Tawny Owl's retina has about 56,000 light-sensitive rods per square millimetre (36 million per square inch); although earlier claims that it could see in the infrared part of the spectrum have been dismissed.[31]​

Cada retina de búho tiene una única fovea.[29]​

Adaptations to night vision include the large size of the eye, its tubular shape, large numbers of closely packed retinal rods, and an absence of cones, since colour vision is unnecessary at night. There are few coloured oil drops, which would reduce the light intensity, but the retina contains a reflective layer, the tapetum lucidum. This increases the amount of light each photosensitive cell receives, allowing the bird to see better in low light conditions.[2]​ Owls normally have only one fovea, and that is poorly developed except in diurnal hunters like the Búho Campestre.[30]​

Besides búhos, Milano Murcielaguero, podargos and añaperos also display good night vision. Some bird species nest deep in cave systems which are too dark for vision, and find their way to the nest with a simple form of echolocation. The Guácharo is the only nocturnal bird to echolocate,[32]​ but several Aerodramus salanganas also utilise this technique, with one species, Salangana de las Cook, also using echolocation outside its caves.[33]​[34]​

Aves acuáticas

Los charranes tienen gotitas de aceite en las células cono del ojo para mejorar la visión a distancia.

Seabirds such as charranes y gaviotass that feed at the surface or plunge for food have red oil droplets in the cones of their retinas. This improves contrast and sharpens distance vision, especially in hazy conditions.[2]​ Birds that have to look through an air/water interface have more deeply coloured carotenoid pigments in the oil drops than other species.[18]​

This helps them to locate shoals of fish, although it is uncertain whether they are sighting the fitoplancton on which the fish feed, or other feeding birds.[35]​

Birds that pursue fish under water like alcas y colimbos have far fewer red oil droplets,[2]​ but they have special flexible lenses and use the nictitating membrane as an additional lens. This allows greater optical accommodation for good vision in air and water.[7]​ Cormorants have a greater range of visual accommodation, at 50 dioptres, than any other bird, but the kingfishers are considered to have the best all-round (air and water) vision.[2]​

Cada retina de Pardela Pichoneta tiene una fovea y una banda alargada de alta densidad de receptores.[29]​

Tubenosed seabirds, which come ashore only to breed and spend most of their life wandering close to the surface of the oceans, have a long narrow area of visual sensitivity on the retina[1]​ This region, the area giganto cellularis, has been found in thePardela Pichoneta, Petrel de Kerguelen, Pardela Capirotada, Pato-petrel Piquiancho y Potoyunco Común. It is characterised by the presence of ganglion cells which are regularly arrayed and larger than those found in the rest of the retina, and morphologically appear similar to the cells of the retina in gatos. The location and cellular morphology of this novel area suggests a function in the detection of items in a small binocular field projecting below and around the bill. It is not concerned primarily with high spatial resolution, but may assist in the detection of prey near the sea surface as a bird flies low over it.[36]​

The Pardela Pichoneta, like many other seabirds, visits its breeding colonies at night to reduce the chances of attack by aerial predators. Two aspects of its optical structure suggest that the eye of this species is adapted to vision at night. In the shearwater's eyes the lens does most of the bending of light necessary to produce a focused image on the retina. The cornea, the outer covering of the eye, is relative flat and so of low refractive power. In a diurnal bird like the pigeon, the reverse is true; the cornea is highly curved and is the principal refractive component. The ration of refraction by the lens to that by the cornea is 1.6 for the pardela and 0.4 for the paloma; the figure for the pardela is consistent with that for a range of different nocturnal bird and mammal.[37]​

The shorter focal length of pardelas eyes give them a smaller, but brighter, image than is the case for pigeons, so the latter has sharper daytime vision. Although the Pardela Pichoneta has adaptations for night vision, the effect is small, and it is likely that these birds also use smell and hearing to locate their nests.[37]​

It used to be thought that pengüinos were short-sighted on land. Although the cornea is flat and adapted to swimming underwater, the lens is very strong and can compensate for the reduced corneal focusing when out of water.[30]​ Almost the opposite solution is used by the Serreta Capuchona which can bulge part of the lens through the iris when submerged.[30]​

Notas

  1. ↑ a b c d e f g h i j Güntürkün, Onur, "Structure and functions of the eye" in Sturkie (1998) 1–18
  2. ↑ a b c d e f g h i j k Sinclair (1985) 88–100
  3. ↑ White, Craig R.; Norman Day, Patrick J. Butler, Graham R. Martin (July de 2007). «Vision and Foraging in Cormorants: More like Herons than Hawks?» (PDF). PLoS ONE 2 (7): e639. PMID 17653266. doi:10.1371/journal.pone.0000639. 
  4. ↑ Martin, Graham R.; Gadi Katzir (1999). «Visual fields in short-toed eagles, Circaetus gallicus (Accipitridae), and the function of binocularity in birds». Brain, Behaviour and Evolution 53 (2): 55-66. PMID 9933782. doi:10.1159/000006582. 
  5. ↑ a b c d e Jones, Michael P; Pierce, Kenneth E; Ward, Daniel (April de 2007). «Avian vision: a review of form and function with special consideration to birds of prey» (PDF). Journal of Exotic Pet Medicine 16 (2): 69–87. doi:10.1053/j.jepm.2007.03.012. 
  6. ↑ Williams, David L.; Flach, Edmund (March de 2003). «Symblepharon with aberrant protrusion of the nictitating membrane in the snowy owl (Nyctea scandiaca)» (PDF). Veterinary Ophthalmology 6 (1): 11–13. PMID 12641836. doi:10.1046/j.1463-5224.2003.00250.x. 
  7. ↑ a b Gill, Frank (1995). Ornithology. New York: WH Freeman and Co. ISBN 0-7167-2415-4. OCLC 30354617. 
  8. ↑ The bird: its form and function. Henry Holt & Co, New York. 1906. p. 214.  Parámetro desconocido |unused_data= ignorado (ayuda)
  9. ↑ a b c Brooke, M. de L.; Hanley, S.; Laughlin, S. B. (February de 1999). «The scaling of eye size with body mass in birds» (PDF). Proceeding of the Royal Society Biological Sciences 266: 405–412. doi:10.1098/rspb.1999.0652. 
  10. ↑ Martin, Graham. "Producing the image" in Ziegler & Bischof (1993) 5–24
  11. ↑ Thomas, Robert J.; Székely, Tamás; Cuthill, Innes C.; Harper, David G. C.; Newson, Stuart E.; Frayling, Tim D.; Wallis, Paul D. (2002). «Eye size in birds and the timing of song at dawn» (PDF). Proceedings of the Royal society of London 269 (1493): 831–837. PMID 1690967. doi:10.1098/rspb.2001.1941. 
  12. ↑ Hall, Margaret I. (June de 2008). «The anatomical relationships between the avian eye, orbit and sclerotic ring: implications for inferring activity patterns in extinct birds». Journal of Anatomy 212 (6): 781–794. doi:10.1111/j.1469-7580.2008.00897.x. 
  13. ↑ Nalbach Hans-Ortwin; Wolf-Oberhollenzer, Friedericke; Remy Monika. "Exploring the image" in Ziegler & Bischof (1993) 26–28
  14. ↑ a b The effect of the coloured oil droplets is to narrow and shift the absorption peak for each pigment. The dotted line shows the unmodified peak for pigment 445. Pigments 508 and 565 would show a similar effect, but the unshifted versions are omitted for clarity.
  15. ↑ a b Basado en Goldsmith (2006) Error en la cita: Etiqueta <ref> no válida; el nombre «ref8» está definido varias veces con contenidos diferentes
  16. ↑ a b c d e f Goldsmith, Timothy H. (July de 2006). «What birds see» (PDF). Scientific American: 69–75. 
  17. ↑ Wilkie, Susan E.; Vissers, Peter M. A. M.; Das, Debipriya; Degrip, Willem J.; Bowmaker, James K.; Hunt, David M. (1998). «The molecular basis for UV vision in birds: spectral characteristics, cDNA sequence and retinal localization of the UV-sensitive visual pigment of the budgerigar (Melopsittacus undulatus)» (PDF). Biochemical Journal 330: 541–47. PMID 9461554. 
  18. ↑ a b c d Varela, F. J.; Palacios, A. G.; Goldsmith T. M. "Color vision in birds" in Ziegler & Bischof (1993) 77–94
  19. ↑ Bowmaker, J. K.; Martin, G. R. (January de 1985). «Visual pigments and oil droplets in the penguin, Spheniscus humbolti». Journal of Comparative Physiology 156 (1): 71–77. doi:10.1007/BF00610668. 
  20. ↑ Goldsmith, T. H.; Collins, J. S;. Licht, S. (1984). «The cone oil droplets of avian retinas». Vision Research. 24 (11): 1661–1671. PMID 6533991. doi:10.1016/0042-6989(84)90324-9. 
  21. ↑ Muheim, Rachel; Phillips, John B. Åkesson, Susanne (August de 2006). «Polarized light cues underlie compass calibration in migratory songbirds» (PDF). Science 313: 837–839. PMID 16902138. doi:10.1126/science.1129709. 
  22. ↑ Greenwood, Verity J.; Smith, Emma L.; Church, Stuart C.; Partridge, Julian C. (2003). «Behavioural investigation of polarisation sensitivity in the Japanese quail (Coturnix coturnix japonica) and the European starling (Sturnus vulgaris)». The Journal of Experimental Biology 206: 3201–3210. PMID 12909701. doi:10.1242/jeb.00537. 
  23. ↑ Andersson, S. (1998). «Ultraviolet sexual dimorphism and assortative mating in blue tits». Proceeding of the Royal Society B 265 (1395): 445-50. doi:10.1098/rspb.1998.0315.  Parámetro desconocido |coathors= ignorado (ayuda)
  24. ↑ Bright, Ashleigh.; Waas, Joseph R. (August de 2002). «Effects of bill pigmentation and UV reflectance during territory establishment in blackbirds» (PDF). Animal Behaviour 64 (2): 207-213. doi:10.1006/anbe.2002.3042. 
  25. ↑ Viitala, Jussi; Erkki Korplmäki, Pälvl Palokangas & Minna Koivula (1995). «Attraction of kestrels to vole scent marks visible in ultraviolet light». Nature 373 (6513): 425-27. doi:10.1038/373425a0. 
  26. ↑ Mouritsen, Henrik; Gesa Feenders, Miriam Liedvogel, Kazuhiro Wada, and Erich D. Jarvis (2005). «Night-vision brain area in migratory songbirds». PNAS 102: 8339-8344. doi:10.1073/pnas.0409575102. 
  27. ↑ Mouritsen, H.; G.Feenders, M.Liedvogel, W.Kropp (2004). «Migratory Birds Use Head Scans to Detect the Direction of the Earth"s Magnetic Field». Current Biology 14 (21): 1946-1949. doi:10.1016/j.cub.2004.10.025. 
  28. ↑ Heyers D, Manns M, Luksch H, Güntürkün O, Mouritsen H (2007). «A Visual Pathway Links Brain Structures Active during Magnetic Compass Orientation in Migratory Birds.». PLoS ONE 2 (9): e937. doi:10.1371/journal.pone.0000937. 
  29. ↑ a b c Diagrama esquemático de retina de ojo derecho, basado someramente en Sturkie (1998) 6
  30. ↑ a b c d Burton (1985) 44–48
  31. ↑ Hecht, Selig; Pirenne, Maurice Henri (1940). «The sensibility of the nocturnal long-eared owl in the spectrum» (Automatic PDF download). Journal of General Physiology 23: 709–717. doi:10.1085/jgp.23.6.709. 
  32. ↑ Cleere, Nigel; Nurney, David (1998). Nightjars: A Guide to the Nightjars, Frogmouths, Potoos, Oilbird and Owlet-nightjars of the World. Pica / Christopher Helm. p. 7. ISBN 1873403488. OCLC 39882046. 
  33. ↑ Fullard, J. H.; Barclay, R.M.R.; Thomas D.W. (1993). «Echolocation in free-flying Atiu Swiftlets (Aerodramus sawtelli)» (PDF). Biotropica 25: 334–339. doi:10.2307/2388791.  Retrieved 12 July 2008
  34. ↑ Konishi, M.; Knudsen E. I. (April de 1979). «The oilbird: hearing and echolocation». Science 204: 425–427. PMID 441731. doi:10.1126/science.441731.  Retrieved 12 July 2008
  35. ↑ Lythgoe, J. N. (1979). The Ecology of Vision. Oxford: Clarendon Press. pp. 180–183. ISBN 0198545290. OCLC 4804801. 
  36. ↑ Hayes, Brian; Martin, Graham R.; Brooke, Michael de L. (1991). «Novel area serving binocular vision in the retinae of procellariiform seabirds». Brain, Behavior and Evolution 37 (2): 79–84. doi:10.1159/000114348. 
  37. ↑ a b Martin, Graham R.; Brooke, Michael de L. (1991). «The Eye of a Procellariiform Seabird, the Manx Shearwater, Puffinus puffinus: Visual Fields and Optical Structure». Brain, Behaviour and Evolution 37 (2): 65–78. doi:10.1159/000114347. 

Referencias

  • Burton, Robert (1985). Bird Behaviour. London: Granada Publishing. ISBN 0246124407. 
  • Sinclair, Sandra (1985). How Animals See: Other Visions of Our World. Beckenham, Kent: Croom Helm. ISBN 0709933363. 
  • Sturkie, P. D. (1998). Sturkie's Avian Physiology. 5th Edition. Academic Press, San Diego. ISBN 0-12-747605-9. OCLC 162128712 191850007 43947653. 
  • Ziegler, Harris Philip; Bischof, Hans-Joachim (eds) (1993). Vision, Brain, and Behavior in Birds: A comparative review. MIT Press. ISBN 026224036X. OCLC 27727176. 
Obtenido de «https://es.wikipedia.org/w/index.php?title=Visión_de_las_aves&oldid=25680382»