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Crinkly brown oak leaves danced across the path. My bike tires swished satisfyingly through drifts of leaves on the ground. Up ahead, a small flock of blue jays swooped across the road one at a time, perfectly complementing the brilliant blue sky. After landing safely in the brush, they cried a harsh “Jay! Jay! Jay!” in alarm at my approach.
Cheerful feeder friend, or wily villain? These big, noisy, gregarious songbirds have quite a varied reputation. But historic accounts of their villainy—like John James Audubon’s painting of three blue jays sucking another birds’ eggs, and his accompanying quote: “Who could imagine that selfishness, duplicity, and malice should form the moral accompaniments of so much physical perfection!”—are now known to be overblown.
While blue jays may occasionally raid the nests of other birds for eggs and nestlings, one study examined the stomachs of 530 blue jays and found traces of eggs and nestlings in only 6. That’s 1.1%. It seems that other species fared quite a bit better than those 530 blue jays.
Even when blue jays eat such non-endearing foods as sunflower seeds and cracked corn, they can get a bad reputation for bullying and gluttony at the bird feeder. By imitating the scream of a red-tailed hawk or red-shouldered hawk as it approaches a food source, a blue jay can scare off other birds and hog the food. For a while. It seems that the other birds figure it out pretty quickly and return to feed.
In some cases, though, the blue jays’ raptor imitations and alarm calls may indicate that a predator is nearby--very kindly warning all the species in the area about shared danger. Plus, having a big, brightly-colored bird with a moveable crest at the feeder was super exciting when teaching my toddler nephews about birds. They learned pretty quickly to identify “downy, gol-fin, jun-co,” and several others while I held them up to see the birdfeeder. But no other bird elicited the childish excitement of “bu-jay!”
I didn’t confuse the toddlers by telling them that blue jays don’t truly have blue feathers. If you hold a feather from a blue jay, bluebird, or indigo bunting in front of a light, it looks brown. This is caused by melanin, a pigment that also makes feathers stronger and more resistant to wear. The blue is really structural color.
The tiny barbs on blue jays’ feathers are actually made of three layers. Light passes easily through a transparent outer layer into box cells. As the feather was growing, thread-like keratin molecules in the box cells separated from liquid. When the cells died, the liquid was replaced by air and the box cells remained filled with a structure of keratin cells and air pockets. This structure causes the red and yellow wavelengths of incoming light to interfere and cancel each other out.
Blue wavelengths are amplified and reflected back to your eye. Small differences in the keratin patterns result in different shades of blue. In some parrots, yellow pigment overlies the blue-ing structures and creates green.
A layer of dark cells filled with the pigment melanin underlies the box cells. These dark cells enhance the blues we see, and also create the striking black patterns on jays’ faces that may help them recognize each other. What’s even more amazing is that the precise nanostructures that allow for blue birds have evolved independently in many unrelated species. Also, this is the same basic science of red and yellow-light absorption and blue-light scattering that explains why the sky looks blue.
So perhaps I shouldn’t poo-poo the colorful, common blue jay. They are said to have complex social systems, mate for life, and use tools in captivity. Their mysteries are not all solved, either. The flock that crossed in front of me may actually be migrating. But only about 20% of blue jays migrate, and the ones that do may not migrate every year. Birdwatchers at Hawk Ridge in Duluth, MN, count blue jays along with migrating raptors. On September 16th, 2013, they counted 5,627 blue jays, bringing the season total of southbound birds to about 25,000. And yet, many stay behind as our feeder friends all winter long.
The movements of blue jays may even be responsible for the oak leaves dancing on the wind and rustling on the road. Ten thousand years ago, a barren Wisconsin had just emerged from under a mile of ice. From pollen samples in the soil, we know that nut-bearing trees like oaks moved back north much faster than trees with wind-blown seeds. Blue jays, who can carry 5 acorns at a time, airlifted the seeds north, cached them under the leaf litter, and essentially planted us a new forest.
With climate change once more altering our landscape, perhaps blue jays will again help move oaks and hickories north to fill in where other less heat and drought tolerant trees may die out. Cheerful feeder friend, or wily villain? Maybe neither one does justice to the beautiful, tree planting blue jay.
For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! The current exhibit, “Nature’s Superheroes—Adventures with Adaptations,” opens in May 2014 and will remain open until March 2015.
Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.