A bird's 'natural' world is a light environment, and exposure to natural sunlight, whether direct or filtered through clouds or leaves, is essential for the wellbeing of birds. Sunlight is made up of light of differing wavelengths and each of the component parts has a role to play in the visual and metabolic health of birds.
Birds kept in outdoor aviaries, or exposed to regular periods of unfiltered sunlight will receive the benefits of sunshine and should not require any additional lighting. For those pet birds, primarily but not exclusively parrots, kept indoors failure to receive adequate levels of unfiltered sunshine can lead to both physiological and psychological disease; these birds do require special lighting.
What is sunlight? The sun emits a range of electromagnetic particles of varying wavelengths; some of these give us visible light and some we are not able to see. One of these ‘invisible’ wavelengths is ultraviolet light (UV) and exposure to a certain level of UV-B is essential for the general health of birds. The light that is emitted from domestic lighting comprises only a limited range of radiation concentrating on the visible spectrum and is lacking in UV-B. Much of the ‘invisible’ radiation spectrum is filtered from reaching potential receivers by a range of products; the ozone layer protects planet earth from over-exposure, sun-blocker protects our skin and window glass whilst allowing visible light to penetrate, blocks the transmission of UV-B. Keeping a bird in a well-light room, whilst making for a pleasant environment does not permit exposure to UV-B. Housed birds are deprived of the natural healthy levels of UV-B light and so this should be provided, as part of good bird husbandry by additional specific, special lighting.
Exposure to UV-B provides many essential benefits to pet birds. Some of the important ones are highlighted below.
Vitamin D3 is required for the active transport of calcium from the gut into the body and for its deployment throughout the body’s organs. It is best known for its role in the development of healthy bones. In non-meat-eating birds such as parrots, vitamin D is obtained from plant material (usually in the form of inactive D2 where it occurs in limited amounts) or, in case of pet parrots, from foods developed to include this (such as formulated diets) or dietary vitamin supplements. Vitamin D3, however, can also be synthesised from the action of UV-B on cholesterol present within the fatty layer of the skin. This is why vitamin D is often referred to as the ‘sunshine vitamin’. One of the benefits of allowing the body to produce its own vitamin D – as opposed to feeding a D3 synthetic supplement - is that there is a control mechanism on its production (a feedback mechanism) that prohibits excess synthesis. Hypervitaminosis D, toxic levels of vitamin D in the body, has been reported and is generally associated with over supplementation.
The majority of parrots come from areas of the world with high UV levels; their bodies have evolved in the presence of these levels. As well as the direct effects that sunlight has on the bird’s metabolism it has been shown that exposure to regular periods of UV-A and UV-B has a beneficial effect on the psychological wellbeing of the bird. Behavioural disorders such as feather-plucking, self-mutilation, screaming and biting and non-natural traits such as lethargy, ‘depression’, reluctance to play or talk, have all been improved in some birds by the use of full spectrum lighting (though such behaviours can often be multi-factorial). There could be a parallel with birds deprived of UV light and SAD sufferers in humans where the brain needs exposure to quality light levels (reaching the brain through the eyes), in order to produce adequate levels of the chemicals that promote psychological, as well as physiological wellbeing.
Birds, unlike humans, have the ability to see colours within the ultraviolet spectrum. What this effectively means is that they have another colour in their visual paint pot (other than shades of the red, green and blue that we see), with which they perceive their world. The natural world puts this to good use. Many birds’ feathers reflect light within the UV-A range and birds that we might perceive as monomorphic, when viewed under UV light have reflective patches. Whilst birds probably do not need help to distinguish males from females, the quality of their respective partners is important and UV-reflectance could be a quality marker for bird breeding. Fruit and berries also take on varying levels of UV reflectance depending on the stage of ripeness. This helps with food assessment and foraging activity. Non-access to a UV-light (full spectrum) environment deprives birds of these areas of their life strategies by depriving them of one of their visual 'senses'.
In short, ensuring that your birds have access to unfiltered full spectrum lighting makes for a happier and healthier bird.
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