Feathers –Part 2

by Mike Stiles

Last month we talked about the form and function of bird feathers. This month we will continue on this vast and varied subject.

Most birds have many thousands of feathers. Most of the visible feathers are called contour feathers and are organized like overlapping roof shingles providing insulation and waterproofing.

Underneath the contour feathers, the fluffy down feathers have no hooks or shafts and give the bird incredible insulation against the cold. Filoplumes have a simple hair-like shaft and often protrude beyond the contour feathers to provide the bird a sense of touch, and may also help a bird determine its airspeed.

Bristle feathers are found on the head and neck and serve a sensory purpose much like the whiskers of a dog or cat. They also protect the eyes from debris on the woodpeckers, and aid in food gathering for the birds that catch insects on the wing.

When a feather begins to grow it emerges as a small knot encased in a sheath that grows outward from the feather follicle. When the feather reaches full size, the blood flow stops, and the feather no longer has living cells. A feather pulled by accident will immediately start growing a replacement, but a worn or broken feather will have to wait to be molted and replaced.

Molting is an incredibly complicated subject and will not be discussed here, but one interesting fact is that for some birds, the change from the drab winter or basic plumage to the sometimes brightly colored breeding plumage is not due to molt, but to feather wear. The dull feather tips and edges simply wear away to reveal the bold alternate plumage underneath.

Feathers have allowed birds to rule the sky, but there are also some incredible adaptations “underneath” the feathers that have aided that feat.

The skeletal structure of birds is highly adapted to allow birds to do what they do. Many bird bones are reinforced hollow structures that provide strength with little weight. The entire skeleton of the frigatebird is half the weight of its feathers. Birds have up to three times the amount of vertebrae compared to mammals.

This allows them to reach every part of their body to preen the all-important feathers.

The lungs of birds are among the most efficient on earth, and are connected to air sacs in the muscles and even into the bones. Sparrows have shown no ill effects in test chambers that simulate 20,000 feet in altitude, and a Ruppell’s Vulture was once killed in the engine of a jetliner at 36,000 feet. The wing beat and hinged ribs compresses the lungs and aids in ventilation.

A bird’s heart is proportionally larger than the mammals, and is stronger and pumps faster. A hummingbird has a heartbeat of one thousand beats per minute, and birds that migrate have larger hearts than non-migratory birds.

Anyone who has spent time outdoors has no doubt found feathers on the ground and wondered just what bird lost them. I admit I have always had trouble trying to discern the species of bird that lost that small piece of evidence, even though I am well acquainted with our local avifauna. I know birders that can tell me what species it came from, whether it’s a flight or tail feather, or even if it was molted or plucked out.

Much of the information in this article comes from the book “Bird Feathers, A Guide to North American Species” by Scott and McFarland, and a great portion of the book is dedicated to feather identification.

I recently found a pile of feathers (see photograph) that, after working through the measurements and photos in the book, lead me to believe are from a Green-winged Teal. Left to right, the feathers are a primary and secondary wing feather, a tail feather, and a feather from the flank of the bird.

The interesting part of the story is that the feathers were found under a tree about a hundred yards from the bird’s habitat on Morro Bay. I can only guess that the duck might have met its fate in the talons of a Peregrine Falcon.