Friday, March 2, 2012

shake ya orange-colored rectrice

Last night, my significant other took me to my first real-live concert in Atlanta. We had floor tickets, meaning we were right up close to the stage (I could see Thom Yorke’s eyeballs). My first real, indoor concert was a success- they even played my favorite song. I was on a Radiohead high as we left.

Once we got back to the car, I began to notice that everything sounded sort of muted. Kind of like when you have a cold and sounds are muffled and dull. After expressing concern that I might be having a stroke or spontaneously going deaf, he explained that it is normal after concerts to experience this. Jeez, the music didn’t sound that loud to me. Hearing is more sensitive than we think.

Notice the bright yellow tail tip (
A group of 6 birds let me know this morning that my hearing was back. As I left my apartment for work, I heard the soft wheezy calls of Cedar Waxwings perched way up high in a tree. These birds used to provide me cheap amusement during my ornithology labs when I was a senior. There were a bunch of big burly dudes in the class who could never hear the Cedar Waxwings calling. The TA would point out the wheezy sound, and everyone would turn their heads in the direction of the birds to get a better listen. The guys dressed in camo, turning their heads furiously (but not so fast as to sling out their dip) would try hear what everyone else did. But they couldn’t- years of hunting with loud guns had destroyed their ability to detect sounds in such a high frequency range. The poor guys will never be able to enjoy the Waxwing’s call.

I’ve mentioned Cedar Waxwings before- I think they are the bees knees. They are very pretty, and the crests on their heads makes them all look like little bird royalty. They are called Waxwings due to waxy-looking red structures that decorate the tip of their wings. Another pretty attribute are the tips of their rectrices (fancy word for tail feathers)- which were usually a bright yellow. However, a curious thing started to happen in the mid 1960’s. Some Cedar Waxwings’ rectrices turned orange.

When birds have red, yellow, or orange colors, it’s due to pigments called carotenoids. The tricky part about carotenoids is that they cannot be manufactured by the body. Vertebrates simply do not have the physiological machinery to make them. So then, how do birds show colors based on pigments their bodies cannot make? Answer: they eat them.

Birds acquire carotenoids via their diet, usually from brightly colored berries that contain carotenoids. When people started looking in to the orange-tip phenomonen, they found that it coincided with the introduction of a new species of honeysuckle whose berries contained a red carotenoid pigment called rhodoxanthin (road-oh-zan-thin). Come to find out, the orange tips were a result of the consumption of these newfangled red berries. New red carotenoids and the standard yellow carotenoids make orange. Pretty cool, eh?

I had never actually seen an orange-tipped Waxwing, until recently. And I didn’t even see the bird. I found three feathers out in the woods with strikingly beautiful yellow-orange tips. It was one of the most gratifying discoveries I’ve ever made. Technically, it is illegal to be in possession of any migratory bird’s feathers due to the Migratory Bird Treaty Act. So I definitely did not take them. And this is definitely not a picture of them. And I definitely don’t sleep with them by my bed.

This is a cool paper that breaks down the tail tip coloration story:

Evidence supporting a dietary basis for orange-tipped rectrices in the Cedar Waxwing by Mulvihill, Pakres, Leberman, and Wood. Journal of Field Ornithology, Vol. 63, No. 2, Spring, 1992.

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