This isn't entirely taxidermy related but last fall I bought some wood ducks and other ducks from a local breeder to try to raise some on my own - yes, I have the paper work, anyway, when I bought them, they were in full color and I was sure to get some reference pics particularly of the red eye ring, they are now going thru their molt or eclipse I guess it's called, and the other day I was surprised to notice that all 4 of my drake wood ducks now have YELLOW eye rings. I seem to recall a post about this a while back, about some one getting a woodie with a yellow ring.. the general response was that this can be found "on occasion" but now its got me wondering if perhaps this is a normal yearly event, part of their eclipse..not that anyone would want to mount one in this condition, they look terrible now..but their eye rings are definetly yellow, not even a tinge of red...thought this was interesting..
Have a good day
TJ
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TJ, I think you will find the big influencing factor of spectrum colors in the red/orange/yellow end of reflected light in the animal world to be caused by carotene and related structures.
These are large molecules that are stored with lipids (fats) in the skins. When the system calls for them, they are transported from the skin with a lipid, into the liver, where a common conversion is the sythesis of vitamin E. Usage of the stored carotenes can result in a "washed out" color.
An absense of a dietary carotene source can prevent the color from occuring, or showing.
The most abundant common source of carotenes for aquatic life, either as a direct, or indirect source, would no doubt have to be cyanobacteria, the blue-green algaes. The blue-greens are composed of a relatively high percentage of glycogen (animal sugar, or "Brain Sugar", the most highly utilizable sugar form for animals), amylopectin (amylose, the plant version of the animal sugar being contained within), and carotene.
The "Classic" example of dietary carotene absence is in captive flamingos. If they are not fed a food that contains carotene (such as shrimp, where the shrimp have eaten the algaes), they wash out to a pink tinted white. Now you know why the pink plastic lawn flamingos turn white after time..........they aren't getting their carotene.
I was just checking to see if you were still paying attention.
Back to dietary sources of carotene. It seems to me that there has been "some" work done on commercially prepared animal/bird foods in the past few years. Tetra Werks out of Germany was the first that I know of to work in this area with fish, years ago. All the ingredients they used at that time were naturally occuring, and expensive. BUT, their products really did the job.
I was told that there had been a "color food" developed for the reptile people, primary use being for iguanas, and turtles. You might check into that, and see if that could possibly work with your feeding program. I'm not sure, but I think there either is, or it is in developement, a color food for cage birds.
but I don't think their diet would be the cause for this, with them being pen raised their diet varies only slightly..In addition to the regular feed which they have been given daily since I bought them, I give them grass, fruits and vegetables, and bread when I have the extra to give them...
I'm curious if any other people out there that raise woodies have noticed this?
I'll be sure to mention the lack of carotene to the neighbor with the "white" flamigo in their lawn LOL~~ they already think we're nuts.. :)
TJ
It is common for there to be wide variation in color like you described. There are many factors that can and do cause this variation.
Same holds true for eye color itslf to vary in birds. People often ask questions on this site about what color is an eye on a pheasant, etc......................just depends on where, the season, diet, and many other factors too numerous to mention. Pheasants for example, I have seen yellow, straw, red, orange and brown eyes!
Seymore
I think I remember Newmyer had an article in Breakthrough and mentioned that this happens in the spring.