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Which Came First, Feathers or Flight?
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From PBS and National Geographic

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A layman tries to come to grips with raptor evolution

In the Winter of 2008
, when we first had significant numbers of educational raptors in outside enclosures, the mercury plunged one night in February to minus 29 degrees. I wasn’t worried about the migratory raptors, as they all have thermostatically controlled, heated bird houses, but I couldn’t sleep, worrying about our Great Horned Owls and other non-migratory residents, so at 2:00 AM, I put on my thick winter coat, donned a head lamp, and went outside to have a look.

Utah, my favorite great horned owl, and frequent glove companion during many presentations, had lost his wing at the wrist, in a collision with a car in Utah the year before, and had become a non-releasable education bird, sent to us by our friend Debbie, who runs a rehab facility called “Second Chance”  (http://wildliferehabilitationinutah.blogspot.com). While I walked out to the large enclosure Utah shared with a female named Artemis, I noticed Cree, our wolf hybrid, tucked into a ball in the corner of his enclosure, with the end of his tail covering his nose. I remember thinking to myself, now this is cold, and I half expected to hear the air freeze in place, fall and shatter on the path before me. To my surprise, Utah was perched in his usual place, out in the weather, nowhere near the wind-curbing overhang and roosting box, where Artemis had sought shelter, and he looked at me like I was the one who might need respite from the cold. Now, I'm not a biologist, but this was a lesson I took to heart.

Like most folks, I long assumed that feathers had developed slowly over time to enable flight, but I’d never really considered how this would happen. The Creationist taunt, “what good is half a wing?”, seemed like a reasonable question.  A fossilized archaeopteryx, which means “ancient wing”, and who lived in the late Jurassic period, about 150 million years ago, was discovered in Germany 150 years ago, about the time Darwin explained how Natural Selection was the driving force behind Evolution. The crow-sized archaeopteryx had a mouth full of teeth, claws for grasping and a reptilian tail, but it was also pretty clear that this was an animal that flew, and since its feathers were not dramatically different in shape from the feathers of modern birds, it was christened the first bird.

Twenty years ago, paleontologists began discovering that many theropods,  the  saurischian dinosaurs who walked on their hind legs, were feathered. Theropods included some herbivores and omnivores, but are more generally associated with fearsome carnivores, like Velociraptor and Tyrannosaurus,  stars of the Jurassic Park movies.  Furthermore, some of these theropods predated archaeopteryx, and their feathers, unlike those of archaeopteryx, were symmetrical, meaning that they would not have assisted in providing the lift that enables flight.

Their wrist bones, however, had evolved in a fashion that allowed them to whip their long clawed fingers forward, presumably to grab prey with, but also in a manner that would become the flight stroke in modern birds. Many of these theropods were also hollow boned, a feature that would make them lighter, adding speed to both their hunting and fleeing capability. At some point, mutations must have produced asymmetry in the feathers, which aided in gliding by providing lift. As natural selection works, the possessors of these feathers were better suited to escape from their unsentimental, larger theropod cousins, analogous to how flying fish escape their pursuers, and they could leap a bit higher in pursuit of prey, glide a bit further, and as a result, they were more likely to survive and pass these feathers along to their offspring.

Okay, back to Utah and that cold Adirondack night. Vertebrates are animals with backbones, and it turns out that feathers, which are composed of one of nature's plastics, beta-keratin, a stiff fibrous protein also found in talons, beaks, and reptilian scales and shells, are the best vertebrate insulation ever, even superior to mammalian fur, which is sort of ironic, since mammals would be supplanting the large dinosaurs wiped out when that big comet decided to cool off in the Gulf of Mexico at the end of the Cretaceous, 65 million years ago. The hair, nails and claws of mammals contain alpha-keratin, a less complex fibrous protein.

In addition, we all know that feathers can grow in a variety of colors, so they’re great for display purposes. Raptor females are almost always larger than males, and approaching males are as likely to be attacked by the object of their affection, as to have their amorous advances indulged. Colorful feathers allowed males to woo females from a safe distance, but also could be displayed to warn other males to back off. Even in nature, threats of violence are safer and less counterproductive than an actual attack, which could seriously injure both males. In other words, feathers provide an example of a feature which evolved for one purpose, in this case, heat retention and further on, display, but with the lengthening of flight feathers and their evolving asymmetrical shapes, ended up enabling flight, as well as the survival of those raptors who could glide or fly.

Meanwhile, some large scary birds survived with those birds who are the ancestors of our modern birds. In fact, for a stretch from 60 million years ago, right up until about 2 million years ago, not long after our ancestors began climbing down from trees, and homo habilis began gradually fanning out of Africa,  the 7 foot tall, 400 pound “Terror Bird”, developed into the velociraptor of it's day, becoming the dominant predator in South America, up until the appearance of saber-toothed cats. The terror bird had a beak the size of an NFL player’s helmet, and huge talons which could disembowel the unfortunate ungulates and plains dwelling creatures it caught up with.

The evolution of today's birds of prey, scaled down to a size commensurate with the smaller creatures they prey on, masks a remarkable evolution, and a link to a past when their ancient ancestors ruled the earth for nearly 150 million years.

Steve Hall

Feather Types and Functions from Cornell Lab of Ornitholgy

Archeopteryx, left, and an example of a "Terror Bird", in this case, Paraphysornis

Feather structure & how oil affects feathers

How does the oil spill, and other forms of contamination affect a birds feather's,
 and their chances of survival? Courtesy of   International Bird Rescue
& The San Francisco Chronicle

International Bird Rescue Research Center

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