The Spread gene "S". 

"Spread, what is it and how does it work"? 

"What exactly is this genetic term and how does it relates to pigeon genes and color effects"?

A typical Blue/Black Spread.

Look at a normal pigeon, be it brown, blue or ash-red and you see both light and dark pattern markings.    By normal, I mean one that isn't being modified by some gene such as almond, grizzle, indigo, opal etc. or the gene we are discussing here known as "Spread".   In other words, a barless, bar or one of the checker patterns.  Add spread to the genetic makeup and you get a solid or self colored bird.  But the genetic term for spread has more than one meaning and to fully understand what this S gene does we need to also understand all three spread terms.

Lets take a plain blue bar pigeon.     The black wing tips and black tail bar are both caused by pigment granules being distributed evenly.     On the basic genetic pattern markings of a barless, a bar or the various checker patterns, this pigment distribution at the wing tips and tail bar is called "Smooth spread".   (This description of Smooth spread is very important, so please read it, again.)    Here light is absorbed by the pigment with very little being reflected back to us.     When this happens we see black.     Smooth spread it is not a gene, its  just a description on how pigment is distributed and ultimately displayed to give our pigeons their genetic pattern markings.   The black markings on the wing shield which make for bars or checker patterns are similar but  pigment distribution here is of a courser distribution and is referred to as "Course spread".     (This description of Course spread is also very important, so please reread it.)    Both smooth and course spread look dark to the naked eye for the same reason, i.e. light reflection.     The remainder of the body, wing shield, upper tail and back have their pigment clumped together in varying degrees to produce lighter or darker shades of blue.   So the various ways a pigeons pigment is dispersed will result in the way light reflects color and marking patterns.

Genetically, a pigeon's wing shield pattern will be either a barless, a bar or one of the various checker patterns.  This is even true when they don’t show any of these basic patterns.   When this happens, some other gene is modifying either the pigment amounts, the shape of the pigment granule or the way it is being  dispersed to cause the overall appearance to hide the true color or basic pattern.   

In addition to the two descriptions of smooth and course pigment distribution, there is also a gene that will change this distribution to a smooth spread in areas where smooth spread is normally not found.  This gene is called "Spread" with the genetic symbol of S.  

OK how does that work?  Well for me to explain it you must first understand how pigment is displayed on a normal, un-modified, color pattern.  Before we do that, let me state that all white markings are the result on no pigmentation being present.  It is a separate issue and for the time being we will not address it.    Let's save white for another time and take a plain blue bar again and begin there. 

When we look at a blue bar pigeon we clearly see what appears as two colors, that is light bluish gray and black.  However, is that what really exist there in the feathers?  Answer NO.  All the pigment found on a blue pattern pigeon is black melanin and it occurs in the form of rod-shaped granules placed parallel to the long axis of the feather barbules.  The way these rod shaped granules are arranged, determines the amount of light that is allowed to reflect back to the viewer's eye.  The more light absorbed the darker the image.  On the other hand, the more light reflected, the lighter or in this case, the more bluish gray that the color appears to our eyes. 

So what determines this arrangement of granules?  For starters, the pattern gene will result in the pattern arrangement of these rod-shaped granules, which in turn produces what we see.  In this case, a bar pattern gene has resulted in our blue bar pigeon. 

OK, so if we substitute granules for color just what would a blue bar look like granularly?  Let us start at the head and work down. The head, neck, wing shield, rump and tail are defined as being bluish gray areas.  Here the melanin rod-shaped granules are all clumped together and not as evenly distributed.  As light strikes the feather, little is absorbed by the pigment and most of the light reflects back as bluish gray in varying degrees depending on both the amounts of pigment present and the manner in which it is dispersed. 

The pattern marking of the wing shield (bars and or checks) as stated above are classified as Course Spread with the melanin rod-shaped granules being evenly distributed.  Since this even distribution results in smaller un-pigmented areas more light is absorbed and little if any light is reflected giving us the appearance of black. 

The tips of the wing feathers (remiges) and end bar of the tail also have melanin rod-shaped granules evenly distributed but as stated above, these areas are classified as Smooth Spread.   Both Course and Smooth Spread areas on a blue appear as black. They both appear that way for the same reason i.e. pigment granules being evenly distributed to cause a reduction in light reflection.  

Joe Quinn in his book, An introduction to Pigeon Science, describes it this way.  " I, at times, think of (S) as an anti-clumping factor.   It just stops development of blue, and regardless of the pattern of the bird, all the feathers will be of the color of the bar on the blue pigeon.   We have previously stated that the amount of black pigment is the same in the blue and the black areas, but that the blue areas have the granules in a clumped fashion producing an optical blue-gray.   This mutation just unclumps these granules (or more properly, prevents their natural clumping) so the entire bird is a self or solid black."  Joe Quinn.  

A genetic friend of mine, Franklin Estabrook; of Wimington, MA. sums it up this way.  "This gene, whether in the heterozygous (single gene) or homozygous (two genes) state, has the same effects on the overall body coloration.   Take the case of the Blue colored pigeon.  The introduction of "Spread" modifier causes the black melanin to be evenly distributed over the entire bird, giving us the appearance of one solid black color.   This same effect is to be found in the Brown family of colors; but in the case of Ash-Red, this effect on color has something entirely different taking place. As Quinn so stated in his book, " (birds may come in this family from the darkest mahogany to the lightest lavenders.)"  Removal of the "Spread" modifier gene from a bird will result in the return of the overall body markings and coloration that had been modified."  Franklin Estabrook. 

Frank Mosca, in one of his excellent genetic articles coined the description of Spread as taking the color of the bird's tail bar and spreading it over the entire body.  This is a very good, yet simplistic description.  It helps you to envision what color a bird would look if spread were added on either a brown or a blue bird.  However, it will not apply to an Ash-red.  This is due to the color effects being different between the smooth and course spread areas of ash-red.

So why is there a difference between these three base colors?   To learn why, we must once more look at the different ways pigment is displayed.  Remember we have Course Spread and Smooth Spread.  Course Spread is pigment evenly dispersed to produce what we find on the tail bar and wing tips.   Smooth Spread is similar in even distribution and is found on the pattern markings.  Pigment found on the remainder of the body is clumped together to give a much lighter color effect.      

The gene for Spread is a modifier of these three normal pigment distributions. The Spread gene causes pigment on a pigeon’s body feathers to be dispersed evenly in the same fashion as the pigment displayed on the Smooth Spread areas of the tail bar and wing tips.  On a blue, both Smooth Spread and Course Spread are displayed as solid black, on a brown they are both dark brown.  Since the Spread gene causes the clumped pigment areas to become evenly distributed like the wing tips and tail bar we end up with a self colored bird.  Therefore, a spread blue or a spread brown becomes a self-solid colored bird assuming nothing else has turned the pigment off to cause white.

From the above we would assume that a spread ash would also be a solid colored bird but in reality, it is not.  On Ash-red the Course and Smooth Spread areas are displayed in the same way as they are on a blue or a brown.  However, the color effect is different.  Course Spread (pattern areas) is seen as red while Smooth Spread (wing tips and tail bar) is seen as an ash color thus the name Ash-red.  The clumped pigment areas continue to be seen as a light color, in this case ash.    The effect then, is that Spread-Ash is less uniform in color.  The course spread areas of the wing bars and checker patterns of Ash-red is where the red pigment is displayed and the even distribution of the pigment granules is not enough to mask the red color, while the other areas are ash and continue to be seen that way .  Both Spread-Ash bar and barless pattern birds are seen as a self-colored Ash and both are often called Barless Ash.  A checked patterned Spread-Ash with its additional amounts of course spread will continue to display red pigment in the wing shield areas but is a less defined pattern.   This phenotype is often called a Strawberry.

Let me sum up in the way I began.   When you look at a normal pigeon be it brown, blue or ash-red you see both light and dark pattern markings.    By normal, I mean one that isn't being modified by some gene like almond, grizzle, indigo, opal or the gene we are discussing here known as spread etc..

Lets take our blue pigeon as an example.     The black wing tips and black tail bar are both caused by the pigment being distributed evenly.     In the pattern marking, this distribution is called "smooth spread".  Here light is absorbed by the pigment with very little being reflected back to us.     When this happens we see black.     Smooth spread it is not a gene, its just a description on how pigment is distributed and ultimately displayed to give us the birds genetic pattern marking.  The black marking on the wing shield that make for bars or checkers is similar but the distribution of pigment there is of a courser distribution and is referred to as "course spread".     They both look black to the naked eye and for the same reason, i.e. light reflection. They are caused differently with one being smooth distribution the other course distribution.    The remainder of the body has its black pigment clumped together in varying degrees to produce lighter or darker shades of blue.    

When you add the gene known as "Spread" it prevents the normal clumping of pigment in a fashion similar to that found in smooth spread, thus the name "Spread" for this modifying gene.  As a gene Spread changes the overall appearance from one of pattern to one of a solid self color.   On a brown or a blue pigeon you get solid brown or black.   On ash-red, the effect of spread varies depending on the amount of course spread present.  The phenotype will vary from a barless ash mealy to a strawberry ash-red.   The more pattern the more strawberry seen. 

 Here are examples of Spread on the different base colors and some of their color modifiers.

Brown Grizzle Spread                                             Brown, Indigo Spread

 Dilute Blue Spread                                                     Blue/Black Spread

Ash-red, checker pattern Spread                                             Ash-red, bar pattern Spread

Brown Spread that is sun faded.                                             Dilute Brown Spread

Reduced Blue Spread.                                             Dom. Opal Blue Spread.

 Recessive Opal Blue Spread cock.                                                     Recessive opal Blue Spread hen

 Dilute Blue Qualmond Spread.                                                     Blue Indigo Spread (Andalusian)

 spread                                                    spread