The male Cardinal glided into my garden. I marveled at the brilliant plumage as he flew from post to fence to the bird feeder. I wondered about that blaring red color. I wondered what made it so, very, very red? I wanted to know the scientific explanation of the what caused such saturation. So, I began to search for the answer and learned some fascinating details about cardinals and urban landscapes.
I heard the pink feathers of a flamingo comes from the foods the bird eats. I understood how that would work in a flamingo eating red crustaceans but I couldn’t figure out what local seeds a seed-eating bird like a cardinal would eat, that would create such an eye-popping red color? I thought about the black-oiled sunflower seeds, flower seeds, and tree seeds that make up the cardinals diet and none of these seeds are red in color. Something else must make the cardinals red color. But, each book I read used the flamingo as an example and didn’t speak about other birds.
So, I turned to scientific articles and here is what I found out. Just like paint from a tube, pigments make up the colors of a bird’s feathers. Feather colors come from pigments or are created by special features of feather surfaces.These pigments are called biochrome pigments, which are naturally occurring chemical compounds. There are three biochrome pigments that occur in bird feathers: melanin, porphyrins and carotenoids.
Melanin is present in all forms of animal life including humans. It is a substance derived from the amino acids which living beings including humans, get from their food. Melanin is found in hair, irises of eyes, fur, skin, feathers, scales, etc. Melanin gives humans our skin and eye colors of a wide rainbow of shades of tans, browns, grays, and blacks. All birds have melanin in their feathers which produces the earth tones of grays, blacks, browns and buff colors.
Porphyrins, an organic chemical compound, produce bright brown, green and magenta colors. Porphyrin is an unstable element and is easily destroyed by sunlight. Porphyrins are fairly common in the reddish and brownish feathers of owls and bustards.
Carotenoids produce red, yellow, and oranges. Carotenoid pigments can accumulate in the body and be modified and used by the body in different ways. Sometimes carotenoids are stored in egg yolks, body fat and as oil gland secretions.
For cardinals, their bright red color is highly dependent on their diets. Cardinals get carotenoids from the seeds and fruits they eat. In cardinals, carotenoids can accumulate in the cell of growing feathers and depending on a few factors, will appear as a bright red color in the plumage of a male cardinal.
In scientific studies, male cardinals were feed a seed-heavy diet without the heavy fruit-based diet that they eat during the molting season. Without wild fruit in their diet, the red plumage was less brilliant and less shocking. The seeds, even though they aren’t red in color, contain the organic compound carotenoid. The “wild”, fruit which contains even more carotenoids than yellow seeds, help create brilliantly red cardinals.
So, the fruits and berries that cardinals eat may contribute heavily to the deep rich red plumage that we see during the breeding season.
See also The Relationship Between Birds, Berries and Fruit
Cardinals are known to do well in urbanized areas. It is thought the cardinal does well because of increased fruit resources primarily from exotic and invasive fruit species (such as multiflora rose and Amur honeysuckle), abundance of bird feeders, more nesting sites in shrubbery and small trees, and warmer winter temperatures caused by conditions such as the abundance of concrete. Studies have shown that urban landscapes, contain nearly three times the amount of fruit and nearby bird feeders than in rural areas. Surprising? I think so.
All of this points to yet another reason to plant native fruit-bearing trees and shrubs. So, when you fill up your seed feeders and plant fruit-bearing trees and shrubs, feel good you are doing a harmonious and life-enhancing act.
My next post will be a list of fruit-bearing shrubs and trees to plant in your yard and garden.
The Dawn Chorus – the Cardinal sings at the break of dawn and in the evening.
Male cardinals and female cardinals eat the exact same diet. So how to explain the differences in color between the two?
Hi Fred, thanks for the comment. Human males and females can eat the same diet and their bodies will be different. I think it just boils down to genetics, sex differences, and DNA.
Hi Donna! I found your article in a Google search after seeing a male and a female cardinal eating the red calyxes of a Seven Sons tree outside my window! I was wondering whether this was common behavior for cardinals related to maintaining their color. Very interesting!
Hi Barbara, I’m glad you found your answer.
Donna, I just read your article when I looked up what makes male cardinals so red. Since I started working from home as a result of COVID-19, I decided to put bird seed out on my balcony. I was getting mostly sparrows and chickadees, so I changed the food to try to attract other birds, including cardinals, and it worked! I love the vibrant red of the cardinals and their crest and beak. I also now have some red finches. I find the bird activity fascinating — so does my indoor cat! I live in Washington, DC. Best, Debra
Hi Debra, I’m glad you found the information useful. Cardinals are in my top 100 favorite birds. Did you hear about the eye disease affecting the birds? https://donnallong.com/mysterious-eye-disease-affecting-the-birds/. You can disinfect you feeders with a 10% bleach solution. Regards, Donna
Thank you for this wonderful article Donna. I spent a lot of today watching pelicans dive into the ocean for fish, and have now spent several hours reading through some of your studies on different natural phenomenons that people like myself often wonder about but usually don’t bother to follow through on. I share your fascination with the natural world, and admire your initiative in creating a blog to post about the different things that tickle your mind. I hope everything is well for you and your loved ones during this difficult time 🙂
Hi, William – Thanks for the supportive words. I am glad you find the blog useful. We are well and you stay safe, too.
Ha! I’d always wondered about this too, but never followed through with research to find out the answer. Thanks for sharing such a thorough explanation.
You’re welcome Madison.
You’re more than welcome.
Donna, thank you for your thorough explanation on how male cardinals have at times such beautiful red feathers. I found your article fascinating. So interesting to learn about the organic chemical compounds – melanin, porphyrins and carotenoidsI love birds and often observed them in my garden.
Thank you Marlene.
Everytime I research how or why something happens I am awed by the wonder of the life all over again. The fascination with this world never, ever gets old.
(Forgive me for not including the proper accent with your name – I don’t have access to it in the reply section.)