[New] Amazing Redbirds!

By now, I trust that most of your holiday festivities have waned and that the serious business of getting through the long winter is at hand. I know that January and February are a real letdown for some, but for me, these quiet, cold months provide a perfect time for cocooning indoors, snuggling with furry pets, and enjoying quiet, peaceful moments. My morning routine consists of a warm cup of coffee, the New York Times crossword, and checking out the neighborhood wildlife from my front picture window.

Many typical Michigan winter scenes offer the stunning contrast of a cheery Northern cardinal perched on a snow-covered branch. Breathtakingly beautiful, it never fails to make me smile. I love spotting a cardinal! Even though they are yearlong residents here in Michigan, they are especially welcome sights in the winter, when their bright scarlet plumage is a pleasant change from the drabness that seems to permeate the deep winter months.

Cardinals are large, migratory songbirds characterized by sexual dimorphism, with males and females displaying different physical characteristics. Bright red feathers distinguish the male, with more tan, drab coloration in the female. Both sexes have short, strong beaks that are orange in color, long, broad tails, and distinctive crests atop their heads. They are highly territorial, so the cardinals you see in your yard are likely the same ones you enjoyed last summer and perhaps the summers before. The birds announce their presence with a distinctive, but familiar song that sometimes sounds like they are calling “cheer-cheer-cheer” in rapid succession. Pairs are serially monogamous, remaining together for a year or longer, and some couples mate for life.

Scientists believe that the bright color of the male is a critical selection trait in attracting a partner. It advertises his ability to provide resources and defend his territory from competing males. According to researchers, more vibrantly red males have been shown to have better immune systems. Field studies in Sweden suggest that males of various bird species possessing the brightest red coloration are more attractive to females. She can infer, from coloration, that the male is physically “fit.” According to a fascinating study, his hue provides vital clues that he is well-fed, strong, capable of protecting the nest and surrounding territory, and well-equipped for winter survival. These are critical considerations that help ensure good conditions to raise future offspring.

I wondered how variation in coloration could be so important. Fortunately, ornithologists, scientists who study birds, have been delving into the biochemistry of bird diet and coloration. Many people have heard that flamingos owe their characteristic pink plumage to shrimp, a favorite foodstuff. The bird takes up the shrimp pigment, hence the similar coloration. In fact, the pink color comes from the consumption, by the shrimp, of carotenoid pigments produced, in minuscule quantities, by algae that make up the diet of the crustaceans.

You may have heard of carotenoids concerning human diets. This lipidbased group of pigments provides the color responsible for yellow, orange, and red fruits and vegetables. When we’re told by health providers to eat foods of many colors, it encourages us to take in these potent antioxidant compounds that are precursors to some of our essential micronutrients, notably vitamin A. This vitamin is critical to, among other benefits, eye health, reproductive success, and immune system development.

As is true for the flamingoes, cardinals (males in particular) owe their brilliant scarlet color to the carotenoids they ingest as part of their diet. A hearty dose of carotenoids in the fruits and seeds they eat is converted biochemically from the yellowish hue of seeds into the striking red color that is the trademark of the cardinal species.

The science that underpins these avian inferences is fascinating! Carotenoids accumulate in bird blood, specifically in the mitochondria. To hark you back to your high school biology, you may remember that the mitochondrion is the “powerhouse of the cell.” It is in this organelle that nutrients are converted to cellular energy. You may also recall that, at least in mammals, red blood cells don’t contain them. Not so in birds! According to Audubon.org, red blood cells in birds are full of mitochondria, which are, in turn, full of carotenoids, red in color. So – the bird’s feathers are a reliable advertisement of his ability to convert the chemical bonds in food/fuel to the cellular energy necessary to support a developing family, whether providing food for his mate and fledglings, protecting territory, or even surviving the harsh winter.

Even after teaching biology for thirty years, there’s still so much that amazes me! I can’t sit back and enjoy these frosty mornings without wondering about something (and frequently many “somethings!”). At present, the Michigan Department of Natural Resources is requesting that residents suspend the use of backyard bird feeders to slow the spread of avian influenza. Even the birds are subject to pandemic pathogens! When the time is right, however, if you’re motivated to set up a feeder to help our local cardinals and other feathered friends, consider stocking a feeder with seeds and nuts high in fats. Safflower seeds, peanuts, and Nyjer (thistle) are exceptionally high in carotenoids, but other sources of proteins and fats abound. A word of caution, though. Please make sure that high-fat bird food is fresh. The natural tendency of nuts and seeds to turn rancid is high, and we don’t want the little birds to have upset tummies! Welcome to 2023! Enjoy our beautiful winter wonderland and stay safe!

Cheryl Hach Retired Science Teacher Kalamazoo Area Math and Science Center

References:

Heinsohn, R. (2005, September12). Why are male birds more colorful than female birds? Environment. https://www.scientificamerican. com/article/why-are-male-birdsmore-c/

Stein, M. (2020, June 22). For Male Cardinals, the Redder, the Better. BirdNote. https://www.audubon. org/news/for-male-cardinals-redderbetter

Bird blood is a heating system in winter. (2021, April 9). Science Daily. https://www.sciencedaily.com/ releases/2021/04/210409104242.htm

MDARD Urges All Michiganders to Continue Protecting Against Highly Pathogenic Avian Influenza. (2022, November 10). Michigan Department of Agriculture and Rural Development. https://www. michigan.gov/mdard/about/media/ pressreleases/2022/11/10/continueprotecting-against-highly-pathogenic-avian-influenza