Fantastic Feathers

A Snowy Owl in flight

My favorite dreams are those exhilarating, flying dreams in which I ‘swim’ effortlessly through the air. So, I understand the passion that is captured by the Greek myth of Icarus who soared on the wings his father Daedalus fashioned from feathers and wax. (Unfortunately for  Icarus, he flew too close to the sun and fell to his death after the wax melted and released the feathers that kept him aloft.)

Birds have perfected the fine-tuned ability to fly over millions of years, so they don’t suffer the high-flying fate of Icarus;1 in fact, some geese have been observed flying over Mount Everest. Their enviable ability to fly relies upon several factors, the first and foremost being the engineering marvels called feathers.2

It is not only fine feathers that make fine birds – Aesop

Nevertheless, additional factors like the size of birds’ pectoral muscles (imagine a human with massive pectoral muscles 20-30% of their body weight versus the typical human’s 4%) and the greater efficiency of birds’ lungs compared to mammals make many of birds’ athletic feats possible. Bird flight is anything but effortless, despite the graceful, apparent ease with which birds accomplish it. Reflect upon a Bar-tailed Godwit’s recently-recorded, non-stop flight of 13,560 kilometers (8,435 miles or 324 non-stop, consecutive marathons), or thick-billed murres’ underwater dives to 700 feet, or peregrine falcons’ pursuit of prey at up to 200 mph. What seems like easy soaring is readily seen as the epic feat that it is.

Male Ruby-Throated Hummingbird hovering

Clothes may make the man, but feathers make the bird3

Harlequin ducks shedding water in Maine

Non-feather factors notwithstanding, feathers are the defining feature of birds. They provide waterproofing, insulate against heat and cold, and streamline a bird’s shape for aerodynamic (e.g., the 200 mph falcon) or hydrodynamic (e.g., the diving murre) efficiency. They have a striking array of colors, particularly in breeding birds, that have evolved to attract the opposite sex. In other words, they are a diving suit, arctic parka, sunshade, and Gortex tuxedo4 all in one package.

A bird’s overall shape and color are largely determined by the feathers of the outermost feather layer. These so-called contour feathers range from the myriad feathers covering the body to the stiff yet flexible primary flight feathers of the wings. They are arrayed like shingles on a roof, maximizing their streamlining, aerodynamic, and protective functions. 

Primary flight feather showing barbs, barbules and hooklets
Primary flight feather with unzipped barbs showing barbules and hooklets

Contour feathers are characterized by sail-like “vanes” that flank a central shaft or rachis. The vanes consist of many progressively smaller, feather-like barbs and barbules that are held together by microscopic hooklets. The beauty of this array is the ease with which a bird may rearrange a ruffled feather with a simple zip through its beak. Picture yourself all rumpled, having slept in your clothes – after some quick shakes and pats, you’re set to go.

“It's not much of a tail, but I'm sort of attached to it.” Winnie-the-Pooh

Unlike Icarus’s feather-and-wax wings, a bird’s flight feathers are firmly attached to bones in the wing, ensuring that they maintain their position during flight and won’t catastrophically fall out when executing aerial feats. The attachment points on the bone are marked by “quill knobs.”5
Quill knobs on a bird's ulna
A needle points to quill knobs on a wing bone, the ulna

However, this firm attachment doesn’t mean that the flight feathers are rigidly fixed in position. On the contrary, small muscles and tendons at the feathers’ bases allow for their fine-tuning during flight – the flaps on the wings of airplanes crudely imitate the flight feathers’ abilities.

Don't judge a bird by its cover

Contour feathers are what one usually sees when looking at a bird and provide waterproofing, streamlining, and coloration; however, they are only a part of a bird’s feather arsenal. If you have ever been outside in a cold, torrential downpour with only a raincoat for protection, you know that keeping dry is not enough to stay comfortable. Birds solve this problem with down and semiplume feathers that form their insulation layer. Humans have been creating similar insulation strategies for winter clothing; technology that birds have had more than a 100 million-year head start to perfect.

Semiplume and down feathers
Semiplume and down feathers
Down feathers are beautifully-engineered bits of fluff that lack the hooklets and the long, stiff shafts, leaving the barbs unable to form vanes characteristic of contour feathers. Down is found primarily next to the body’s skin to insulate and help maintain the bird’s core heat, but can also be found on the wings and upper legs.6

Semiplume feather in the wind, trapped on a rhododendron

Semiplume feathers are intermediate between down and contour feathers.  I suspect that rather than there being strict categories of “down,” “semiplume,” and “contour,” there is a more gradual transition between the feather types. We humans like neat categories, but nature isn’t always neat.

Whiskers or feathers?

It is hard to choose favorites among feathers (and perhaps feather favoritism isn’t a great use of mental energy). Still, I am particularly fond of bristles and filoplumes, two unfeather-like feathers that are not often seen and that appear to protect birds and enable them to sense their environment better.

Bristles are highly modified feathers located primarily on the head. Rictal bristles (rictus means “gaping mouth” in Latin) form tiny mustaches around the mouth and may help protect birds’ eyes from struggling prey. Other bristles around some birds’ eyes may serve the same protective function as our eyelashes. Look closely at the next bird you see to find bristles.

Rictal bristles of a Northern Parula
Rictal bristles around a Northern Parula's beak
Filoplume feather
A 4mm long filoplume feather

Another very modified feather that is very hard to find is the filoplume feather which nestles among other feathers on the body and wings and looks like a tiny, ratty broom. Appearances can be deceiving, however, and these feathers are thought to monitor the positions of the shifting feather coat as a bird moves and flies. They may also alert the bird to broken or missing feathers, leading them to be replaced sooner. Currently, filoplume feathers are probably the least understood of all feather types. This is why they may be my favorites – I am just a sucker for mystery, deceptive simplicity, and the suggestion that they oversee the health of other feathers.

 

Filoplume feathers are only a few millimeters long in very small birds to a few inches long in very large birds and are much fewer in number than other feather types.

Relax and enjoy the view7
Peacock feather relaxing on a sofa

Sometimes the beauty in nature blinds you to the beauty in nature. That is, the obvious, in-your-face beauty overwhelms the subtle elegance. Feathers are like that – the overall beauty of a bird can veil the underlying richness of form and function of the individual feathers. Next time you spot a feather on the ground, look closely, and you may see just how amazing it is.

Notes

1 So far, my flying, dream-self has also avoided Icarus’s fate.

2 Be aware that collecting feathers, bones, eggs, nests, or other parts of native North American birds without special permits is illegal under the Migratory Bird Protection Act. Any protected feathers or bones pictured in this essay were photographed as found or were moved temporarily to be photographed. For more information, see https://www.fws.gov/lab/featheratlas/feathers-and-the-law.php

3 According to Shakespeare.

4 I say “tuxedo” because the colorful breeding plumage is usually a characteristic of males.

5 Quill knobs found on some dinosaurs’ bones support the theory that some dinosaurs had feathers and are related to birds.

6 Because down still provides the lightest weight insulation, down may line some cold-weather gear like jackets and gloves. Be aware that there can be significant cruelty associated with down. See Lauren Ferrucci’s podcast on this topic. https://anchor.fm/lauren-ferrucci/episodes/Down-and-Feather-Products-e1oksce  

7 Thanks to Jill Knowles for the miniatures accompanying the peacock feather. Note: it is not illegal to possess Peacock feathers.

References

Thanks

Special thanks to Zoe Weil’s editorial expertise

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jeff
jeff
1 year ago

excellent piece, thanks for sharing;

Rae
Rae
1 year ago

Loved this one…..the hummer video, just wow… And the Harlequin ducks photo is fabulous. I love the quality of the water in that one. Thanks for this! I hope everyone falls in love with birds! This is the only blog I read every time a new one appears.

Zoe Weil
Zoe Weil
1 year ago

Thanks for the shout out on editorial feedback. It’s a privilege to help in any way because these posts are so great. That hummingbird video! WOWZA!

Patty Bergstrom
Patty Bergstrom
1 year ago

Yes the hummingbird video was amazing! I learned so much about feathers too. Keep’m coming!

Megan Harvey Harvey Bourke
Megan Harvey Harvey Bourke
1 year ago

Fun one! Great images!

Nancy
1 year ago

Edwin,
Your photos are amazing….fun to read and educational.
Thank you. Enjoyed our visit.

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