Signs of Spring Update: May 8, 2000 Today's Report Includes: Brilliant Spring Colors! Why So Bright? What if You Turned the Color of the Food You Eat? Try This! Blue: Not What You Think Seeing is Believing How About Those Dazzling Hummers? One Pigment, Many Colors: Challenge Question #16 Do Red-Feathered Cranes Have More Fun? Year-End Evaluation: Please Share Your Thoughts Brilliant Spring Colors! Photo Courtesy Provincial Museum of Alberta Orioles and other colorful migrants are streaming through the continent right now. As if inspired by greening trees and colorful flowers, their feathers seem to be growing in brilliance too. The shining orange of orioles, intense red of tanagers, and bright blue of Indigo Buntings glow in the spring sun. Even the goldfinches that stay in many areas of the continent all winter seem more radiant right now. Which brilliant birds have you noticed in your area? The intense spring colors and vivid patterns give almost all bird species a unique appearance and identity. In most species, like orioles, females are attracted to the most vivid males. The bright colors also help a lot of birds to advertise their territory. Oddly, many male birds feel stressed when they see another male of their species because of these bright colors! When the stressed male is on his own territory, he chases the other away. When the stressed male is not on his own territory, he pulls away from the other male. Why So Bright? Now you know why birds are so bright, but have you ever wondered what gives their feathers such bright colors? Some of the colors are produced by pigments--the same kinds of chemicals that give color crayons or paints their colors. There are only three kinds of feather pigments, but each can actually produce several colors. Melanins are the most common pigments, giving feathers colors from soft yellow through red-brown, dark brown, and black. Carotenoids usually produce yellow, orange, and red. These pigments make orioles so gorgeous! Porphyrins are the least common pigments. They make the African turacos green and red, and give a pink coloring to the bustards of Europe and Asia. What if You Turned the Color of the Food You Eat? Birds usually make their own pigments, but sometimes they get them from their food. So a change in diet can sometimes change a bird's color. Some orioles look more red or yellow than normal, and tanagers may look orange, when their diets have more or less of some fruits. Waxwings usually have a bright yellow band at the tip of their tails, but diet can turn this orange. If flamingoes don't eat enough shrimp, they can't produce the pigment that makes their feathers so pink and they become white. Try This! Write a story about a person who DID turn colors, based on what she ate. Try to use at least 3 new words that you learned in this update. Blue: Not What You Think Oddly, there is absolutely NO pigment to make feathers blue. So how can we possibly have such vivid blue birds as Indigo Buntings, Blue Jays, and bluebirds? Their feathers don't produce that color with any chemical. Instead, the color is produced simply by the way some cells are arranged on the feather. This makes blue a STRUCTURAL color. There are still pigments in the innermost cells of a blue feather, but around those cells are two more layers--cells that produce a blue optical illusion when light hits them, and clear reflecting cells on the outside that make the light reflect back, showing that blue. Seeing is Believing If you can find a Blue Jay feather, see how bright it is when light shines on it. Then hold it up to a light source so light passes through it, and see how it turns brownish gray when you see the true pigment color! How About Those Dazzling Hummers? Photo permission of John Owens The dazzling iridescence in some duck and hummingbird feathers is also structural. The male Ruby-throated Hummingbird's throat feathers have dark melanin pigments, making them black or very dark gray. But the iridescent structural color when light reflects off them is ruby red. Depending on what angle we see them at, a hummer's feathers can switch back and forth, red to black to red again! One Pigment, Many Colors Many parrots, including common pet parakeets, or budgies, only make one kind of pigment, a yellow carotenoid. But budgies can be yellow, green, blue, or white! How do you think budgies can come in four totally different colors? Challenge Question #16: "How can a bird come in yellow, green, blue, or white when it can only possibly produce one yellow pigment?" (To respond to this question, please follow the instructions below.) Do Red-Feathered Cranes Have More Fun? The body and wing feathers of Sandhill Cranes are plain gray due to melanin pigments. But for some mysterious reason, when cranes live in areas with a lot of iron in the soil, they paint their feathers with mud! The reddish iron in the soil soaks into the feathers, turning them brown. Like water-proof makeup, the feathers hold that color even in a fierce rain. But when sandhill cranes molt and lose those painted feathers, the cranes turn gray and stay that color until they can paint their feathers again. No one knows for sure why cranes do this. Any ideas? How to Respond to Today's Challenge Question: 1. Address an E-mail message to: jn-challenge-spring@learner.org 2. In the Subject Line of your message write: Challenge Question #16. 3. In the body of the message, give your answer to the question above. Journey North Year End Evaluation Please share your thoughts The FINAL "Signs of Spring" Update Will be Posted on May 22, 2000. Copyright 2000 Journey North. All Rights Reserved. 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