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Those working with birds in zoological collections, commercial aviaries and poultry farms have long recognized that the behavior and health of the animals under their care seemed influenced by the quality and amount of light that they received. It many cases, breeding behavior and egg production also seemed linked to light in some way. Observant hobbyists also realize that parrots, canaries, finches and a host of other birds seem to do much better when exposed to natural sunlight. Perhaps you have noticed that birds housed in outdoor exhibits at zoos, or observed in the wild, seem more vigorous, active and brighter in color than individuals of the same species kept indoors?
Details concerning the specific needs of captive birds as regards light quality and quantity are still lacking in some respects, but a great deal has been learned. Much of this information has come as a byproduct of the exploding interest in captive reptiles, many of which fail to thrive if not provided with appropriate lighting regimes. We now know that most commonly kept bird species rely upon ultraviolet light of a specific type (UVB with a wavelength of 295-310 nanometers) in order to synthesize Vitamin D (if experience with reptiles is any guide, nocturnal species such as owls and nightjars are likely able to obtain adequate amounts of Vitamin D from their diet). Exposure to UVB in this wavelength is also critical to normalization of the calcium/phosphorus ratio. Birds also sense ultraviolet light of another type, commonly known as UVA, as well as the colors red, green and blue (in this regard they are said to have tetrachromatic vision). UVA light provides the aforementioned colors, when viewed by birds, with a certain "tone" that we humans do not sense. Without UVA, birds will not see these colors properly, and their behavior and health will be negatively affected.
Conveying Light and the importance of UVA and UVB Most birds have a number of ways of assessing the quality and duration of the light to which they are exposed, and of conveying that information to the brain. Details concerning light quality are sensed by the retina and relayed to the pituitary gland. The Harderian Gland, locating near the eye, sends information concerning wavelength and photoperiod to the pineal gland. The pineal gland, thyroid gland and hypothalamus use this information to affect the functioning of other organs and of behavior in general. Insufficient or inappropriate levels of UVB or UVA, and daylight periods that are too long or to short, can lead to a host of problems in the functioning of these glands. So, if the quality of the light is not sufficient (i.e. “full spectrum”, or similar to that supplied by natural sunlight), critical glands will malfunction and will, in turn, negatively affect a number of important organs and processes.
Among the first of such problems that came to the attention of aviculturists was low calcium levels, or hypocalcaemia, most commonly seen in African gray parrots. In the past, the treatment for this condition was to provide extra calcium, but we now know that low levels of Vitamin D, the result of insufficient exposure to UVB light, are most likely the culprit (vitamin D, produced in the presence of UVB, is needed if the bird is to effectively utilize calcium). Lethargy, poor feather growth, failure to preen, skin diseases and even behavioral problems have been linked to the lack of UVB. Exposure to Natural Sunlight With all this in mind, we can see that it is important to give careful consideration to the type and amount of light that we provide to our pet birds. Essentially, what we should be aiming for is the provision of full spectrum light -- light whose characteristics closely approximate that of the sun. Obviously, the simplest way to achieve this is to provide our birds with some exposure to unfiltered natural sunlight each day (I say "unfiltered" because typical window glass filters out about 90% of the beneficial ultraviolet rays. UVB permeable glass is available, but it is quite expensive). If you do put your bird outdoors, be sure that the cage is securely locked and also that it will not come apart if knocked over by the wind or a cat. The cage should be placed in a location that provides some shade, and never directly in the mid-day sun. A well-constructed outdoor flight cage is an excellent option and will add greatly to your pet’s quality of life.
Providing Lighting At Home
Those of us lacking the ability to provide our birds with sunlight exposure must rely largely upon full spectrum light bulbs (note: technical articles will refer to bulbs as “lamps”). A good deal of research has gone into this area recently, and a number of very useful fluorescent bulbs and fixtures are now available. Although you should check the manufacturer's recommendations carefully, most of these bulbs function most effectively when mounted at approximately 2 feet above the bird’s cage. Do not position the bulb closer than recommended by the manufacturer – birds’ eyes are very light-sensitive, and being forced into close contact with bright light will negatively affect their behavior and health. It is also vital that you note the recommended usage time, and mark down the date on which the bulb should be replaced. Be sure to ascertain that the manufacturer’s time recommendation pertains to the emission of UVB, and not to the emission of light in general (the bulbs will continue to emit light long after they have stopped producing UVB). In most cases, bulbs should be replaced at 6 month intervals.
Bulbs manufactured for reptiles should not be used, nor should "high output UVB bulbs" not specifically formulated for birds. Be sure to use a high quality fluorescent light fixture when mounting your bulb, as the ballasts on some models cause the light to flicker minutely so that it emits short pulses of light. You may not be able to sense this, but your bird likely will. If the bulb is positioned at the correct distance from your pet’s cage but the bird seems to be stressed or uncomfortable none-the-less, the fixture may be to blame. Another important lighting consideration is photoperiod, or the length of your bird’s “day” and “night”. Please bear in mind that most birds require 10-12 hours of sleep each night, and that such should be had in a quiet, dark room. Studies indicate that that diets containing certain forms and amounts of Vitamin D may, for certain bird species, eliminate the need for UVB light.
The abstract of an article describing a controlled experiment involving calcium levels in African grey parrots is available at: http://veterinaryrecord.bvapublications.com/cgi/content/abstract/159/8/236