Consider the bird, in all its glorious forms: from the minute hummingbird to the land-bound ostrich; from the brilliantly-colored parrot, to the monochromatic crow; from the predatory raptor to the fruit-eating waxwing. For 135 million years they have walked and flown about the planet. A pretty good-sized portion of the human population has taken to birds like a fish to water, and it is easy to see why – their colors and ability to fly have captured our imaginations.

When you page through almost any field guide to birds, you find that it is arranged in a particular order: from the most ancient species (loons, waterfowl) to the most modern/advanced (the finches). The ancestors of loons and geese paddled around the same waters as many of the last dinosaurs. When the reign of the dinosaurs came to its firey end, many of the birds of that time perished as well, but not the loons and geese, ducks and other shorebirds. These animals lived on and are still with us today. Perhaps this is one reason why we find the call of the loon so haunting. One can almost imagine it calling out through the mists of a tropical world where giant reptiles still roamed.

Feathers seem to be the big thing that sets birds apart from the rest of life on this planet, not flight. After all, birds are not the only things that fly; so do insects. At one point in time, there were reptiles that also flew. Today, some lizards and snakes still take to the air, but they no longer can fly, they merely glide. Still, it is more than you or I can do without the aid of mechanical devices, so we will grant them this point.

It is currently believed that feathers initially evolved not for flight, but as a means of keeping warm. To this day, there are few natural fibers that insulate quite as well as feathers. Birds have six basic types of feathers: flight feathers, contour feathers, filoplumes, semiplumes, bristle feathers, and down. Of course, there is also a substance known as powder down, but it isn’t really a feather, so for now we will ignore it.

Flight feathers are, as you might have guessed, the long, sturdy feathers that make up the working part of the wing. They are asymmetrical: the leading edge, or anterior vane, is narrower than the trailing edge, or posterior vane. Between the two vanes runs the rachis, or shaft, of the feather. These are the real workhorses of the feathers, and they are incredibly stiff because they take quite a beating (no pun intended). When Thomas Jefferson sought a feather for a quill with which to write the Declaration of Independence, it is a flight feather that he used.

Contour feathers are the ones that give the bird’s body its basic shape. Most of the feathers that you see when you are looking at a bird are contour feathers. Like flight feathers (which technically are also contour feathers), they have a pretty rigid shaft, but unlike flight feathers, they are symmetrical. The tip of each contour feather is neat and tidy, but the bottom half is fluffy. This part is closest to the body, where it works to keep the bird warm. Contour feathers are attached to the bird in a way similar to shingles on a roof – each overlapping its predecessor, creating a interlocking, aerodynamic form.

Semiplumes are my favorites. These are the feathers that are made up of long, fluffy strands. Unlike the feathers mentioned above, semiplumes are wild, they don’t lie all neat and tidy. If you were to take a flight or contour feather and rough it up a bit, you would find that you could straighten it easily enough by running y our fingers up the barbs (the individual strands that make up each vane). They “zip” together with little trouble, thanks to the hooks that line their edges. Semiplumes don’t have these hooks, so their “strands” stick out all over the place. Their purpose? Insulation. You’ll find the semiplumes located just beneath the contour feathers.

As you can see, layering is what it is all about. Birds knew this long before we humans picked up on it. Layering, as we all know today, is the best way to keep warm when the weather turns cold, and down is the way to go. Down feathers are naught but tufts of fluff. They trap the most amount of air, creating the best insulating layer. These are the feathers that lie closest to the body, trapping the body’s heat where it can do the most good. Similar to the semiplume, down is wild and untamed in its appearance. Unlike the other feathers, it has no (or nearly no) shaft – it is, as I said, naught but fluff.

Probably of the coolest of the feathers, however, are the fliloplumes. These feathers look like a wand with a bit of fluff stuck to the tip. Filoplumes are located just below, and sometimes sticking out from, the contour feathers. It is believed that they fulfill the same function as whiskers do on a cat: they detect movement and vibrations. It is possible that these feathers help the bird know when it is time to groom – the bird can feel when things are out of place. Another thought is that they might help the bird gauge its speed when in flight.

Bristle feathers are just the opposite of filoplumes in appearance: a bit of fluff near the base and a stiff, tapered shaft at the tip. You will only find bristle feathers on the heads and necks of birds. On some birds they protect they eyes (eyelashes?), and on others they form an insect-catching mesh around the mouth. They are quite prominent around the mouths of whippoorwills, nighthawks and flycatchers.

When it comes to birds, feathers are but the tip of the iceberg of what makes them fascinating. I recently added a new book to my collection of field guides (pretty soon I’ll have to hire a Sherpa just to carry my field guides into the field with me). It is a guide to the feathers of many North American birds. I don’t know about you, but I often find feathers when I go out for a walk in the woods, or even a paddle on the water. Some feathers are pretty easy to identify, but others can sure be a puzzle. With the help of this book I hope to be able to add one more proverbial feather to my naturalist’s cap.