"Why is the flamingo red?" I believe that many people have issued such soul torture to their parents at the flamingo pond in the zoo when they were young.
"Because they eat something that contains red astaxanthin", this is probably the most well-known and accepted "answer". But can an answer score a hundred points? With this question in mind, let's find out!
"Flamingo" refers to a variety of large water birds of the family Flamingo family. Pictured is the American red stork in the zoo. Photo: Ge Zhiyuan
<h1 class="pgc-h-arrow-right" > flamingo's red, where did it come from</h1>
Like many red creatures in nature, red is usually a manifestation of pigment color, and the flamingo's red color is derived from a natural pigment called carotenoids.
There are more than 1,000 known carotenoids in the world, which exhibit different colors from yellow to red due to differences in molecular structure – in simple terms, the longer the conjugate double bond chain (structure of alternating single and double bonds) of a carotenoid, the reddish color it becomes.
Compared to β-cryptoxanthin (left), astaxanthin (right) has longer conjugated double bond chains and is also redder in color. Photo: GE et al. / Carbohydrate
<h1 class="pgc-h-arrow-right" > which red pigments are in flamingos</h1>
The most famous of the red carotenoids is astaxanthin, the mouth-watering red color of salmon meat, and the seductive red color of shrimp and crab after cooking are all masterpieces of astaxanthin.
And flamingos, scientists do find astaxanthin in their feathers and skin tissue, but! Red carotenoids (hereinafter referred to as red pigments) were also found in calendula (adonirubin), canthaxanthin, and Phoenicopterone (Phoenicopterone, which is found only in the three flamingos of the genus Flamingo).
Nortextrin powder. Don't be misled by its name, it's not yellow. Image: taiwan-healthcare.org
<h1 class= "pgc-h-arrow-right" >, is astaxanthin the most</h1>?
Although astaxanthin is not the only red pigment present in flamingos, if its content is dominant, we can still think that the key factor that determines the red color of flamingos is astaxanthin.
However, this hypothesis is once again ruthlessly dismissed by facts.
After quantitative analysis of carotenoids in flamingos, scientists found that although there are certain differences in the composition and proportion of red pigments contained in different flamingos, only in the leg skin of the American flamingo, the content of astaxanthin is dominant. Among other feather and tissue samples, the highest proportion is without exception, and the content of astaxanthin can only be ranked second or third, and the absolute content is far from the first place of keratin.
图片：Amat & Rendon / Flamingos. Behavior, Biology, and Relationship with Humans (2017)
Red carotenoids detected in the feathers and feet of six flamingos (the * sign represents no data).
<h1 class="pgc-h-arrow-right" > how does a flamingo get red pigments? </h1>
It is known that there are no organisms in vertebrates that can produce carotenoids on their own, so food becomes the only source of access to them.
Flamingos, which are mainly filtered, grow a peculiar beak that can sift plankton such as algae and small aquatic crustaceans from the water, and these foods are rich in a variety of red carotenoids, including keratin and astaxanthin. Scientists have also confirmed in the study of the American red stork that when it stopped feeding carotenoid-bearing foods for 6 months, the carotenoid level in flamingos' blood dropped by nearly 90%!
Close-up of the beak of the flamingo of the flamingo genus Flamingo. Image: Zweers et al. / Journal of Avian Biology (1995); tagged by Ge Zhiyuan
But scientists have also found that the flamingos' red pigments don't come entirely from their food! Because when scientists re-added β-carotene (a common foodborne carotenoid) to their food, not only did β-carotene levels in the blood begin to gradually recover, but also an increase in red pigments such as candibaloids were detected — indicating that flamingos can convert other carotenoids into the red pigments they need through biochemical reactions in their bodies.
So in summary, the flamingo has a beautiful red color because it accumulates a large number of red carotenoids such as cartein and astaxanthin, and these red pigments are either obtained directly from food or produced in the body by converting other carotenoids.
<h1 class="pgc-h-arrow-right" > why the little flamingo is not red</h1>
Newborn flamingos have only melanin in their bodies and no red carotenoids, which has a lot to do with the fact that they do not yet have a filter-feeding beak like their parents. As they grow up and their beaks further develop and form, the melanin in their bodies is gradually replaced by red pigment. It takes about 4 to 6 years for a flaming stork to grow into an adult plumage like its parents.
The Great Flamingo stork and its chicks. Image: Wikicommons
<h1 class="pgc-h-arrow-right" > what is the use of turning red</h1>
There are many roles that red carotenoids play in the organism, such as it has strong antioxidant properties, can neutralize free radicals, and helps resist the damage that ultraviolet rays in the sun may cause to cells.
This may be why the Andean Flamingos and James Flamingos, which live at high altitudes, have far higher carotenoid levels than the other four flamingos that live at lower altitudes.
Andean Flamingo. Diego Delso / Wikimedia
As for the saying that "flamingo parents are the greatest, they work hard for their children" stems from the fact that flamingos will feed their chicks a kind of crop milk that is like blood. And what causes this blood-colored appearance is the keratin in the bird's milk.
But interestingly, the chicks did not turn red because of this. Scientists have dissected a 16-day-old chick, but have not found many traces of keratin. Subsequent studies of other chicks have yielded similar results.
Scientists believe that these keratins may be used by chicks in the rapid growth period and have a high metabolism in other places than decorative body colors, but what exactly happens needs to be further studied.
This is not the blood from the broken head, but the red bird's milk that can't be held back. Image: A Broken Red Pen/YouTube
In addition to accumulating red pigment in the feathers, the flamingo secretes red pigment from the tail fat glands during the breeding season, and then applies it to the feathers to make it look more red and eye-catching.
Scientists have found that making themselves look redder seems to make them more susceptible to the opposite sex. This red color seems to be a strong signal, telling the other party that he is the most beautiful cub on the whole lake, providing important reference information for choosing a partner when courtship.
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