Blue. A primary color. One of the most beloved colors. And, speaking of Owl Acres, a rare color indeed, if you don’t count the sky and the blue jays. The sky is blue. But not really. That is, it looks blue because of the way the air molecules in the atmosphere scatter the short blue light waves. There’s really nothing blue there that you could capture and make paint out of, for instance.
Some flowers are blue, but the compounds that make them blue are unstable and short-lived. Indigo and woad are exceptions to this, and have been highly valued for millennia. Lapis lazuli is a blue mineral used to make blue paint, but it, too, is expensive and, alas, not found on Owl Acres.
Most birds get their coloring out of the pigments in things they eat, but there’s nothing blue for the blue jay to eat. So how does one of our most common birds, the blue jay (Cyanocitta cristata), dress himself in blue? The answer is an optical illusion. Blue jay feathers aren’t really blue. Well, they look blue, so I guess they really are blue in that sense. But if you backlight one, or crush it, it doesn’t look blue anymore. It looks brown. It does not have any blue pigment in it at all. Its blueness depends on an optical phenomenon created by the way its feathers are made. It’s the same phenomenon that makes my eyes blue, and it’s called a structural color. Here’s how it works.
Feathers are made of keratin. Each feather comprises a shaft and barbs that are arranged along the shaft. If you look at a cross-section of a barb from a blue jay feather under a microscope, you will see that it has a layer of milky-looking keratin with scattered particles of melanin, a dark brown pigment. The milky appearance is due to tiny air pockets in the keratin. The center of the barb has a layer of melanin honeycombed with more tiny air pockets.
Now, remember that light travels in waves. In a rainbow, the longest waves are at the red end, and the shortest waves are at the blue end of the spectrum. When the short blue waves encounter obstacles or changes of a specific size, like those tiny air pockets and specks of melanin in a blue jay’s feather, they bounce off in all directions. Instead of heading on into the melanin layer in the center of the barb where they would be absorbed, these short blue waves scatter, and are reflected back out of the feather. Meanwhile, the longer waves of other colors like red are absorbed by the melanin in the center of the barb. Since we see what is reflected, not what is absorbed, the blue jay’s feathers look blue. It’s a clever trick of the light encountering the specially designed and arranged medium in the middle of the barbs of the blue jay’s feather. As long as the blue jay feather is intact and has light shining on it, it will look blue.
For now we’ll let Mr. Blue Jay maintain the fiction that he is blue. He is bright blue on his head, back and tail, and sports a gray-blue crest on the top of his head. Underneath, his throat, breast and belly are white. His wings are blue with black and white bars on them. His eyes, bill, legs and feet are black, and he has a black necklace around his throat. The female wears the same wardrobe in a slightly smaller size.
Blue jays are fairly large birds. They average nine to twelve inches long with a wing span of 13 to 17 inches. They are members of the corvid family which includes jays, crows and magpies, and are considered to be some of the most intelligent birds we have on Owl Acres. They are some of the most aggressive, too. Blue jays are very territorial and make no bones about driving other birds away from bird feeders and nesting sites. One tactic they use is to imitate the call of a red-shouldered or red-tailed hawk to frighten the smaller birds away. They are excellent mimics.
Blue jays mate for life after an intense selection process carried out by the female. She perches in a tree, and several male suitors join her. She takes off flying, and the males follow her until she lands again. She does this repeatedly over several hours. Her goal seems to be to tire them out, and the last one standing gets the prize. They’ll mate and work together to build a nest in the crotch of a tree branch 10 to 30 feet above the ground. She’ll lay three to five eggs and incubate them for a couple weeks while her partner brings her food and protects the nest. The nestlings stay in the nest for two months and even after fledging will stay with their parents as a little family for longer periods.
Blue jays are native to North America. Their population is estimated at 17 million, but has been declining about 0.6 percent a year over the past 50 years.
Some blue jays migrate, but the ones on Owl Acres seem to stay around all winter. Their reasons for migrating, and the migratory patterns they exhibit, are not well understood.
We’ll hear them calling their characteristic harsh cries throughout the winter, and occasionally, a flash of blue will decorate the bare branches in the woods.
Photo by Eric LaPrice. Alt text: Bird with bright blue wings and a feather crest perches atop a feeder attached to a tree trunk. Black-edged, light grey face with round black eye. The blue jay grips a seed in its black beak.