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01 October 2009 @ 10:58 am
Discussions on The Eclectus Eyesight  

I would love to see a photo of your Eclectus because lately I'm fascinated with how different they look even though they have so many of the same features. Some of the distinguishing factors we see are perceived by potential mates and add to the selection process. The human eyes are very limited when it comes to actually seeing what parrots see in the wild or on a daily basis and many determining factors of mate selection come from a discerning and advanced perception.

I'd like to post pieces of an email conversation I had that started with a lady whose Eclectus seemed like she was seeing "ghosts" in the room and was scared to be in a particular room. There are different opinions here, but they all agree on the fact that the eyesight of our parrots is incredibly unique and they see colors and lights which the human eye cannot. I would not be surprised if our Eclectus could perceive 'light trails' 'apparitions' 'multidimensional objects' 'multitudes of flourescent and ultraviolet colors' which might sometimes spook them to bits while we wonder what happened. Here are pieces of the conversation, cut for length:

I wanted to mention again that parrot's eyes are constructed much differently than a human's eyes. If you haven't already done so, I would highly recommend the purchase of the book: Manual of Parrot Behavior Edited by Andrew U. Luescher. It is the most recent release of a book every parrot friend and owner should possess. In this book, Vision is explained as "enhanced". (PG. 33) It states that avian species perceive approximately 2 to 8 times higher than mammals. There are a large number of cones present compared to human eyes i.e. a hawk's fovea has around 300,000 cones whereas the human fovea contains around 147,000. "In addition, nearly every cone in the avian eye is represented by an individual axon traveling to the brain while the human eye contains six to seven million cones but only one million axons in the entire optic nerve." Regarding UV light - (PG. 34) "Birds are able to see UV light below 400 nm due to the combined effects of cone oil droplets and visual pigments. While trichromatic color vision in humans is based on three colors (blue green and red) the tetrachromatic, or pentrachromatic in some avian species, system of birds includes UV, fluorescent, blue, green and red. UV perception of parrots likely plays an important role in behavior. Further, birds are able to detect a spatial frequency of around 160 frames per second or hertz compared to 50-60 hertz in humans. Because most artificial lights produce noncontinuous light at a frequency of around 100-120 hz, a stroboscopic effect not detectable to humans results and may be detrimental to birds."


reply to my post:

Luescher is essentially "parroting" some things that have been known for
quite some time--and presenting some figures that are somewhat erroneous.
Persistence of vision (the ability to detect flicker) has nothing to do with
UV or color perception--and his numbers are skewed. Human persistence
begins at 48 CPS--and avian persistence at around 120-140 CPS.

Also, the only birds which may be said to possess "pentachromatic" vision
are certain passerines and nocturnal species. The fifth component is not
"fluorescent", which is a product of ultraviolet, but far red and near
infrared. There are no Psittaciformes that manifest anything except
tetrachromatic vision--nor are able to detect flicker above 130 CPS. The
last line in the quote is sheer garbage--and bears no relation to fact.

The absolute range of tropical bird vision is 370-620nm. The average range
of human vision is 400-700nm. See the graph here for a comparison:

Ultraviolet light is not going to "reveal" any object that is not already
visible to the human (trichromatic) eye--it will however give a shift in the
spectral perception range and cause certain materials to fluoresce or
reflect in ways that are not visible to us.

We have a very good idea of how the world appears with tetrachromatic
vision--as a result of early cataract surgeries which removed the lens and
at the same time UV filtration falling on the retina. An examination of the
work of Claude Monet after 1923 reveals a startling difference in color
perception after his surgery.

Lights which are billed as "UV lights" for vitamin D synthesis are a product
of the reptile keeping world--and from a general perspective are not very
beneficial in the complete provision of light to captive birds. They are
heavily overloaded in the blue end of the spectrum--and sadly lacking in the
middle ranges and often contain little or no red. Extended exposure to
predominantly blue spectral energy has been shown to cause a number of
untoward effects in captive bird populations.

Among the most common are anxiety, aggressive behaviors, reduced immune
response, and hormonal changes in breeding condition birds which result in
predominantly male offspring--as well as heightened hormonal levels. So
yes, the light being left on for five days could be a contributing factor to
what is happening.


My response with his replies:

"That's very informative also and essentially proves my
original point, regardless of what the actual figures are states clearly
that a parrot's vision and perception is different than that of a human's
which is essentially all I was trying to say."

Absolutely, and on several points. The avian eye has a greater
concentration of receptors which allow a more acute, defined view of the
world--along with the absence of certain filters which block near UV and
long wave UVA wavelengths. This intensifies perception, especially from a
distance, and assists in the identification of ripe fruits and grains. This
is an evolutionary adaptation unique to creatures of light and air!

"Ultraviolet light is not going to 'reveal' any object that is not already visible to the human (trichromatic) eye--it will however give a shift in the spectral perception range and cause certain materials to fluoresce or reflect in ways that are not visible to us." ...." it will however give a shift in the spectral perception range and cause certain materials to fluoresce or reflect in ways that are not visible to us." So, technicaly it DOES have
the potential to reveal human-eye unseen content...."

True. I may have misconstrued the "seeing spooks" analogy--but the thrust
is more or less correct. All color (except what is produced by light
emitting devices) is a balance of absorption and reflection. Color
characteristics can change dramatically based upon the composition of the
light that strikes them. Think how different certain clothing colors look
in sunlight, fluorescent light, incandescent light, and metal halide light
like in stores--and how difficult it is to distinguish variations under some
lighting sources. This is where matters of color temperature (Kelvin) and
Color Rendition Index (CRI) come in to play.

Certain materials absorb or reflect UV as well--a process quite different
from fluorescence which for the most part requires no special capabilities
to see. If anything, birds will note a deepening and vibrancy of all
blues--and a darkening of yellows and reds. With reflectance, markings on
wings and variations in natural materials would become visible--and has been
recognized as a basis of mate selection. Additionally, ripe fruits and
grains appear darker due to UV absorption than unripened ones--helping birds
to choose the most succulent and nutritious natural foods. What is quite
interesting is to watch captive bird feeding choices change when provided
with the proper balances of additional lighting in those areas which do not
receive adequate amounts of natural light. Foods they would ignore or
discard now becomes a cherished tidbit! This is one of the first comments I
receive back from my customers regarding changes in bird behavior with avian
corrected lighting solutions.

"I'd also like to get your opinion on the belief that parrots like our Eclectus can see within a whole separate dimension and add to their perception colors of a much wider spectrum."

There are no "new" colors that birds can see that humans cannot--it is all
in how those absorption and reflectance characteristics are remapped by the
sensitivities of particular oil drop filters and cones of the retina. There
are only four characteristics that create a color space; hue, saturation,
luminance, and contrast. As you saw in the perception graph on the B&L
site, our birds do not necessarily have a wider range of spectral
perception--simply one that is shifted upwards somewhat from ours. What
they gain in the UVA spectra--they lose in the red frequencies.

Not only do we have the work of Monet and the verbal histories given by
early cataract patients--technology has provided us a window to look into
the world of tetrachromatic vision--through digital photography. Check out
the photographs on this site. Once in a category, on the left is what we
see with visible light, in the middle the UVA reflectance/absorption
characteristics, and on the right a corrected combination that is very
similar to what our birds see. The main difference is that reds will not
have the range seen here--and the very deepest for the most part will appear
dark grey or black.


"You state --- "The last line in the quote is sheer garbage--and bears no
relation to fact." Which line are you referring to? Why is it sheer garbage
and please explain to me what the facts are. "

My apologies for that--it was rather unprofessional. I write on this
subject in over a dozen other avian lists and forums--along with numerous
special interest groups, forums and blogs--plus research and writing is how
I pay my bills... Sometimes I get a little frazzled over mendacious claims
that do not bear any scrutiny--and contain logical fallacies and weasel
words--such as "most, all, always" etcetera, and then do not provide any
references or explanation to back it up. That's when I get short in my
replies. Otherwise, long posts get longer, and an ever increasing number of
readers fall asleep...


Light Flicker

Ed wrote:

As I understand it, a flourescent light with a magnetic old-style ballast
running at 60 Hz AC produces a 120 Hz flicker - twice the frequency of the
AC, on the Positive and Negative AC cycles. Also the persistence of the
phosphor coating which emits the visable light helps carry the light through
the cycles reducing the flicker. Incandescents can indeed produce some
flicker too. Ever have a strobe disk on a turntable (or record player) in
room with incandescent-only lighting? You will see some stroboscopic effect
even under full incandescent lighting.

Patrick's Response:

Alternating current is a sine wave--meaning one half of a
complete cycle is positive, and one half is negative. It takes 1/120 of a
second for each reversal to complete. It is possible for a single or
multiple fluorescent tubes to exhibit 120 CPS flicker--if it were wired
directly to the line supply or attached to a special kind of ballast. Many
writers take this electrical fact and extend it to mean that this is what a
light is actually doing. It is wrong.

What chucks this factual electrical reasoning in the trash is the
introduction of an ordinary magnetic ballast. A magnetic ballast is an
electrical inductor--meaning that it is a coil of wire wound around a
permeable magnetic core. Inductors have numerous properties--most notably
for our concern the ability to temporarily "store" current in a magnetic
field, and that they introduce a phase shift in AC power between the voltage
and current.

But let's get back to how fluorescent lights work electrically. Inside the
tube, there is a small amount of mercury and mercury vapor under low
pressure argon or xenon gas. When voltage and current (your household
electric) is applied across a tube, electrons are emitted at the ends of the
tube, causing the gas to convert to a plasma. This begins an "avalanche"
effect which draws current across the tube then ionizing the mercury
vapor--and certain wavelengths of visible and UV light are emitted. These
then strike the phosphor coating, and Voila!

The trouble with this picture is that as the gas ionizes, its electrical
resistance decreases and it begins to draw an ever increasing amount of
current. This is called negative differential resistance. It is not a good
thing, for unchecked the lamp will explode in short order. This is where
the ballast comes into play. An inductor is a reactive device--meaning that
as the sine wave rises in either direction a magnetic field (or flux) is
created which in turn induces an electromotive force (EMF) which then acts
in opposition to any change in current. Through this mechanism, the ballast
limits the amount of current being drawn by the lamp and stabilizes it at
functional levels.

Now we come to the point. When the sine wave reaches its maximum potential
on either side of the cycle and begins to decline, the strength of the flux
reduces and collapses at zero amplitude (that point that it begins to
reverse itself) and the EMF stored in the permeable core of the inductor is
released in a half wave action. This results in a phase shift between the
voltage and current, that essentially establishes a current CPS rate in the
tube of 60 hertz. This shift does reduce the power efficiency (Q) of the
ballast, and there are ways to get around that.

Those of us that are hams or electrical souls know that if we place a
capacitor (a device that temporarily stores electrical energy) across an
inductor, we have created a resonant circuit--something that can alternate
storage between the inductor and the capacitor. By doing so we can do two
different things--restore the phase relationship between the line current
and voltage, and shift the timing of the phase relationship between discrete
circuits. Restoring the phase relationship increases the power factor (Q)
of the ballast--but does not change the flux decay phase relationship.

Special magnetic ballasts are made that are called "lead-lag" types. These
are expensive and are used in multiple lamp fixtures. They use a
multi-winding inductor and capacitor array--and by feeding opposite ends of
the inductor produce a situation where one lamp leads the mains phase and
the other lags the mains phase. This then causes a pair (or even number
multiples) of lamps to flicker at 60 hertz exactly 180 degrees out of phase
to each other--creating an apparent 120 hertz rate to the eye. This is a
commercial ballast, and you are not going to find it in a cheap Home Depot
shop fixture or any other common residential linear fluorescent lighting
fixture--unless you spent extra or have put it in yourself. So ultimately,
the bulk of consumer grade linear fluorescent lighting is going to pump out
a 60 CPS flicker.

The "stuff" about 120 hertz flicker is extracted from commercial lighting
manuals and industrial safety environmental science--which presumes the use
of a lead-lag ballast. So the information is right--and at the same time it
is wrong.

As to your simile of the phonographic alignment disk--it is not the light
that induces an apparent stroboscopic flicker--it is rather the tiny
movements of the eye, and a matter called "flicker fusion threshold". The
tungsten filament of these bulbs incandesce anywhere from 3000-5000 degrees
Fahrenheit--even more for halogen types. At the rates we are discussing,
there is not enough time for the filament to cool sufficiently to cause a



final response:

Let me bring this around to context again so that we keep this strictly to the vision of our Eclectus parrots. I have read through the plentiful and fascinating information Patrick has provided and have just a couple questions which arose.

First, I loved the TV Link, Patrick. Thank you for sending that! It states on the page that the human eye connects the black lines that slide up and down to form a constant picture. Seeing what the parrot eye perceives, does the parrot eye also connect the thicker, slower black lines or do they actually perceive the lines going up and down on a CRT screen?

On the link that you sent of the UV photos, which section is most like what our parrots see or are the photos there just to point out how objects look within different light range to the human eye?

Regarding setting up a lighting situation altogether, what system or setup would you recommend for a basic living room with three very large windows and lots of sunlight coming in (though I know that the windows filter out valuable UV light)? I currently have two VitaLite Spiralux bulbs 26 Watts shining down on Kiwi for approximately 10-12 hours a day. I don't just switch these lamps on in the morning. I wait for the dawn to arrive then when it gets lighter I point one of the lamps away from Kiwi for a while to let him adjust to the light then after an hour or so turn the other on and point them toward him from about two feet away.

I read that the white-tinted bulbs aren't beneficial to our birds because they are not truly full-spectrum (and neither are incandescent bulbs claiming to be full spectrum because you can't get full spectrum without fluorescent light) but I thought I also read that the white tinted bulbs can be detrimental to our parrots. Can you tell me why?

And regarding color selection with appropriate lighting. I agree that mates will often be chosen by brilliance of color in the wild and by preference of feather markings however, what is your opinion on those birds that select nearly completely plucked and featherless mates when full-feathered ones are available to choose as well? I have several wonderful stories about this happening in Refuges and Sanctuaries quite often. One amazing story was that of Lola, the amazing Greenwing Macaw, who came from a terribly abusive situation and had brain damage / seizures as a result of years of abuse who then went on to be selected by a full-feathered, stunning male. (( Read her incredible story here - it makes me cry every time. http://www.mpebs.com/our_story_1.html )) Obviously in cases like this, Lola's lack of proper feathering or reflection of light on her plummage weren't an issue. Her husband accepted her for who she was and they bonded completely. Is light always a factor or are we seeing behavior that is advanced and come straight from the emotional aspect of our brilliant parrots?

Also regarding the perception of color -- what is your opinion on which colors might be most stimulating (or aggravating) to our parrots? Is it on a case by case basis or since the parrot eyes are so specifically constructed, does a particular color (or two) cause more stress or response than another? How, then, should we adjust to this, i.e. decorating homes, the clothes we wear, artwork we have, colors of blankets/covers we put on their cages, colors of their toys, etc etc?

Overall, I get the impression that you're stating that a parrot's vision IS different than that of a human's but it's not so detrimentally different that we cause them "strobic" harm with incandescent lighting or by watching a flat screen TV. In it's most basic sense, is this view accurate? (Keep in mind, I agree wholeheartedly that people should provide their captive birds an environment lit as closely as possible to an outdoor habitat.)


It was a very insightful exchange of emails and unfortunately the final response was not provided but all this content is very valuable to think about when we wonder why our Eclectus suddenly took a leap across the living room and we don't see anything for miles around that might have caused them to do so or when they start screaming at the outdoors for no apparent reason and looking like they're ready to take off like a bat out of hell, wide-eyed and terrified.

Current Mood: cheerfulcheerful
elizabethlilostitch on October 1st, 2009 05:25 pm (UTC)
Pictures of Alida after her bath

xela_bird on October 1st, 2009 09:05 pm (UTC)
Re: Pictures of Alida after her bath
she is just stunning.
her beak is so beautiful.
I remember when I used to take Tori's beak in my fingers and kiss it silly. thanks for sharing these great shots!
saloua: лапыsaloua on October 1st, 2009 06:37 pm (UTC)

He is five months old here. Time to take new photos...
xela_bird on October 1st, 2009 09:03 pm (UTC)
Re: Avishai
he is so awesome!
I love his big eyes!