COLUMN: Naturalist notes

     How do birds have such colorful feathers?

     Many of you have observed the beautiful red cardinal and brightly-colored blue jay. Did you ever wonder how they get their beautiful coloration? The answer is multifaceted and depends on the bird being considered. The Cornell Lab of Ornithology has a wonderful website with detailed explanations of bird coloration. I would encourage everyone to check it out when you have time. (https://academy.allaboutbirds.org/how-birds-make-colorful-feathers/)

     Here are a few summarizations of these explanations for our areas common backyard birds.

     The bright red male northern cardinal with his bold ornate head crest is a widely known backyard bird and recognized by many as the mascot of the Iowa State Cyclones. The intensity of the red color of cardinal feathers depends on his diet. Foods, such as fruits, seeds, and insects, high in carotenoid pigments contribute to a greater intensity of red coloration in both the male and female cardinal feathers. Over thousands of years female cardinals have been selective and chosen red males as mates. The degree of redness may indicate to the female the males’ health and ability to retain a good and promising territory.

     The male American goldfinch, our state bird, also acquires his bright yellow colored feathers from the ingestion of foods high in carotenoids; the better the diet the more vibrant the coloration and health of the goldfinch. In addition, if you were to look closely at the individual feathers of a goldfinch you would notice that only the tips of the feathers are actually yellow. The goldfinch’s body feathers overlap allowing sunlight to pass through the yellow tips and reflect off the white feathers below, causing the goldfinch to almost glow yellow. Goldfinches go through a complete molt (shedding and growing new feathers) each fall and a partial molt each spring. This is why goldfinches appear bright yellow during the summer and a drab yellow, much like the females, during the winter. To watch a slideshow of this process visit https://www.sibleyguides.com/2012/05/the-annual-plumage-cycle-of-a-male-american-goldfinch/.

     In the well-known and boisterous blue jay the blue color comes from the structure of their feathers, and not from the pigments they eat. Their feathers are in reality brownish black. The feathers contain microscopic structures of keratin proteins that refract light like a prism. When light passes through the dark layer of melanin in the feathers some wavelengths of light are filtered out causing the blue jay to appear blue. This also happens with indigo buntings and bluebirds.

     Many birds, like the common grackle, have iridescent feathers which, like in the blue jay, are caused by micro-structural features within the feathers. Many rich colors are split from the light when refraction occurs, similar to that of a prism. As the viewing angle changes the refracted light becomes visible with astonishingly glowing color variations.

     Many birds, especially the females who need to be camouflaged when sitting on their nest, are commonly drab in color. This is caused from the melanin pigment, responsible for brown and black color variations. Melanin-dominated feathers tend to be very strong and resist wear and tear; making them a common color of wing and flight feathers. Often all white birds lacking pigment in most of their feathers will have black flight feathers because of their strength and durability.

     Check out the birds in your neighborhood.   If you have a natural resource related question email naturalist@co.jones.ia.us or mail questions to Jones County Conservation, Attn:  Naturalist, 12515 Central Park Rd, Center Junction, IA 52212.