SIMULATING NATURAL PHOTOPERIOD: THE STEPPED LIGHTING APPROACHPatrick R. Thrush © 1999
Scene One. A thick darkness covers the forest floor, and lies in lighter shades along open glades. A fine mist drifts through the top of the tree canopy, and the gentle patter made by droplets of dew falling from the leaves is interspersed with the soft, stealthy activities of the night dwellers. Almost imperceptible, a grey light dreamily creeps in. Nocturnal denizens have already, as if by call, returned to their homes and burrows and begun to settle in for sleep. Other animals now begin to move about the land, foraging and mating. The light grows stronger. Familiar creatures now begin to stir, awakening and waiting for the proper moment to begin their daily routines. The twilight creatures disappear as the sun peeks over the horizon. The forest is awake, the day has begun.
By midmorning, the sun beats down in fullness upon the land. Colors are exposed in all their richness, and many animals, especially birds and reptiles begin their courtship and mating rituals. By mid afternoon the sun begins to wane, colors darken, and activity begins to slow. Gradually, the shadows lengthen, and the light acquires rich hues of yellow, orange and red. The specter of night quickly approaches, encircling all within a grey cloak. The inhabitants of the day are secure for the night, and the twilight calls forth its own. Night falls. Darkness again lies across the face of the world. The cycle of day and night plays itself out in never ending succession.
Scene Two. A fuzzy grey light replaces the darkness of the night. The absolute stillness of the house has been broken for some time by a cacophony of human activity; suddenly with great fanfare, the light above the cage comes on, and the area below is flooded with brilliant light. Activity levels rise and fall throughout the day, but the intensity of the light remains the same. Twelve hours or so come and go, and suddenly, the area is plunged again into darkness. Night has come.
Scene Three. The cage sits in a dark room. Outside, the sun rises, and another day springs anew. But inside the room, light filters weakly through the windows, muted illumination offset by bright patches which move across the floor as the day progresses. No direct light ever falls upon the cage. The day draws to a close, and darkness surrounds the house. Occasionally lights are turned on, spilling pools of xanthic light about them, to be as suddenly and unpredictably turned off. The unnatural flickering glow of the television casts a ghostly pallor on everything in the room. Shadows appear and shift with chaotic frenzy. Finally, all are extinguished. Darkness is the only consistent factor.
Consider these three scenarios. The first one of course, is the natural environment that most tropical birds experience. This is what their biological programming is tuned to make peak use of. Uncountable generations of birds have responded to the cues given by sunlight and atmosphere, and adjust their cycles of mating and nurturing, eating and play, rest and sleep, to coincide with the waxing and waning of the day. It is the normal process of the day which assists in the regulation and maintenance of biological homeostasis (balance).
The second scene is far more common in the life of the captive bird. Unless cages or aviaries are located outside, or in an open windowed environment, there exists an on or off condition of light and daytime. Little except human interaction impinges upon this world, and the avian physiology must make adjustments to this consistent photoperiod. In doing so, it is inevitable that some stress is induced in the organism, as physical reality impinges upon a programmed biological clock that requires gradual changes to bring about natural cycles.
The third condition is terribly unnatural and detrimental to the general health of the bird. It is not always uncaring birdkeepers who develop such practices, mostly those who are uninformed about their bird’s need for light and balanced environment. It is these birds that are most often found to be behaviorally maladjusted, suffering from lethargy, and a plethora of endocrine and nutritional imbalances. Longevity is assuredly decreased, and immune response compromised to where opportunistic infections often occur.
If it were possible, it is this writers belief that most aviculturists would seek to emulate the most natural conditions possible. This would include lots of sunshine and fresh air. But this just not possible in many cases. In response to good stewardship, a considerable percentage of birdkeepers have elected to provided a source of artificial light which is either manually or timer activated. In a survey conducted on avian lighting practice, it was revealed that the majority of aviculturists rely on a fixed daily photoperiod through out the year.
Through his technology, man has thrown aside the constraint of natural photoperiod. The invention of the electric light allows the shifting of normal rhythms to whatever convenient pattern is called for. But lesser creatures have a greater reliance on the ebb and flow of nature. They depend upon a certain sequence of events to assist in their well being and ability to survive. It is this fact which must be considered in its entirety when making a wild creature captive. Birds do not have a long history of species adaptation to technological innovation as do humans. As such, birdkeepers need look toward methods of recreating more natural forms and patterns.
It is toward this overarching concept that this article directs itself. While we cannot create the perfect aviary environment, we can take control of how and of what quality light is provided to birds. To this date, avian lighting science has been an arbitrary and poorly practiced paradigm. Research on the effects of light on the organism are just in their infancy. It is odd that more research has been directed to reptilian forms than birds, but the fact exists that many species of reptile simply cannot survive without special lighting considerations. An unfortunate fallout of this has been the translation of that body of work to a dissimilar form, the bird. With this preamble, I would like to introduce the reader to the concept of stepped (or incremental) lighting.
Retrace the sequence of events in scene one. Darkness gradually gives way to daylight; the intensity and concentration of light rises, peaks, and falls throughout the day; again gradually light diminishes into darkness. Given this chain of events, how would the aviculturist best accomplish the effect of diurnal (daylight) cycle for the inside bird? The answer to this comes in two forms of the stepped lighting paradigm, Single Stepped and Dual Stepped.
In a Single Stepped scenario, timing of electric lighting is offset to allow a natural progression of daylight to occur in the immediate surroundings of the bird. Optimally, systems would not be activated until an hour or so after sunrise, when full daylight is present and has achieved whatever level of interior illumination will be normal for the day. This lighting remains on throughout the day, until approximately an hour or so before sunset, when the system shuts off. This constitutes approximately two to three hours per day of graduated lighting, and between ten and twelve hours per day (depending upon season) of consistent illumination.
The single stepped application of lighting may be accomplished with dual or quad tube fluorescent arrays. As in any fixed ratio lighting application, only fluorescent devices rated at a CRI (Color Rendition Index) of >90, and Color Temperature of 5000-5500K be employed. Devices operating within these parameters deliver the best possible visible and UVA wavelengths to the bird. It should be noted that exposure of the bird to natural sunlight at any time in this period does not affect the timing of either single or dual stepping.
The dual stepped concept may be applied through the use of two single lamp or two dual lamp fluorescent fixtures. The only requirement is that devices are capable of acting independently of each other. As with the single step concept, the first array (primary) switches on an hour or so after sunrise. Approximately another hour to hour and a half later the second unit (secondary) switches on. This cycle is repeated in the evening, with the secondary unit switching off two to two and a half hours before the primary unit. In this manner, birds are exposed to an incremental cycle of light throughout the diurnal cycle.
Using the dual stepped concept, artificial illumination is provided ten to twelve hours per day, seasonally adjusted. With the secondary source delay, equivalency is given to the peak natural sunlight hours of 10:00AM to 2:00PM. It must be noted that in either paradigm, the room location must receive some perceptive and effective level of morning and evening light to maintain equivalency. In those environments which receive little or no sunlight, an hour of early dawn and late evening may be simulated by the use of a small fluorescent utility light, such as the models manufactured for under cabinet use. These should be placed a fair distance from the cage area (such as eight to ten feet) and require no special tubes for use.
Seasonal and Daylight Savings Time adjustments should be made to the timing of either method. A table of these corrections is available at the Birds & Lighting Website. In cases of power outage, readjustment must be made also. In areas which suffer frequent power disruption, it is advised to purchase the digital, battery operated sort of timer that maintains its cycle. Both methods must be timer controlled, or inconsistencies which occur in standard lighting via manual operation offset the benefit of incremental and balanced photoperiod.
In emulating natural light conditions, several beneficial factors are offered to your bird. First and foremost is the reduction of physiological stress. The period of natural dawn and twilight allow the bird to adjust its metabolism in a more gradual manner external triggers. This allows endocrine, digestive, and metabolic states to elevate or decrease in the same fashion experienced in native environments. Secondary is the reduction of psychological stress through balanced photoperiod. Through optic and pineal pathways, light is perceived and transmitted to the brain, where the regulation of brain wave activities results in adequate levels of serotonin and endorphins. This is in opposition to the overstimulation or understimulation given by fixed or absent lighting paradigms.
It is possible that the balance of photoperiod and adequate diet may correct many of the “behavioral” problems experienced by hookbill species. If one considers the effect various forms of deprivation (and proper light period and quality have been numbered among them) have on any higher organism, then the reduction of these factors and the introduction of natural forms can only serve to increase the quality of life experienced. Given this, consider applying one of the stepped lighting paradigms to your next lighting installation or retrofit.
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Copyright 1999 by Patrick Thrush
