Author offers a flock of fascinating details about feathers
They'll be all fluffed up with natal down (feathers), making them appear larger than the adults.
"They look like little linebackers out there," said Thor Hanson, a conservation biologist.
Feathers grow in different forms. A downy feather has a little nub of a quill and fluffy branch strands that act as insulation. The feathers are pushed out by more mature feathers.
Hanson, a San Juan Islands' resident is author of "Feathers: The Evolution of a Natural Miracle" ($16), a fascinating look at the natural and cultural history of feathers, and the winner of the John Burroughs Medal for natural history authors.
Most birds molt at least once a year. Feathers wear out through hard work and because of pests and parasites that degrade feathers over time, Hanson said.
"The physical strain on feathers is the underlying reason, but they can also molt to repair damage in case of a feathered blooper, such as hitting a window."
Another purpose is served by molting.
"It's molting for display, to molt in a set of feathers specifically designed to attract a mate ... to have wonderfully bright plumage ... to signal one's sexual maturity and vigor," he said.
The avian molting process is universal, but there are often different strategies.
"The Virginia rail is dashing about in the grass, constantly rubbing its feathers in the vegetation, and has to molt several times a year," Hanson said,
A large seabird like an albatross has a different approach.
"They can't molt all their wing feathers in one season. They're too bloody big and can't grow fast enough for them to molt, fly and breed at the same time.
"It's a highly energetic process. Anyone who keeps chickens finds it's frustrating to go to the expense of feeding a flock of molting chickens and buying eggs at the store," Hanson said.
Why don't we see more feathers on the ground?
"When birds are molting, they are getting rid of older feathers that are breaking down. They disappear pretty quickly. That's why they are so bloody rare in the fossil records of birds," Hanson said.
It's a marvelous time to be interested in feather evolution.
"A trove of feathered dinosaurs is being discovered. Suddenly there are dozens of feathered species. It's surprising to see how long ago that feathers were fully developed. The oldest feathered fossil is 160 million years old and had modern-looking plumes at that stage of evolution," he said.
Hanson is fascinated by some of evolution's tweaks, including feathers to generate sound.
"The club-winged manakins' feathers are specially adapted. A manakin 'plays' its feathers like a violin during courting (by beating its wings over its back)," Hanson said.
In addition to denser bones than other birds, it has some oddly shaped secondary feathers on its wings, some with barbs that are next to some with ridges. The combination generates a tone.
The structures of feathers are incredibly diverse. Some absorb water, others repel water; some are incredibly aerodynamic, others are not; some are for display, others are not.
There are wings that generate sound loud enough so that we can hear them fly by, such as a raven's. Other feathers are built to minimize sound, as are an owl's.
"As a consequence of microstructures on the surface of the wing, certain sounds are made. An owl has feathers with special adaptations, long barbs to disturb the airflow to silence flight. But you can hear every wing beat of a raven."
The most amazing thing about feathers is their diversity, Hanson said.
"When you look at the adaptations, there are all kinds of incredible feathers designed for a single purpose. There's almost nothing else that serve so many purposes as well," he said.
Columnist Sharon Wootton can be reached at 360-468-3964 or www.songandword.com.
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