Fly tiers are some of the most knowledgeable people in regard to feathers because of their extensive and innovative use of feathers in the fishing flies they tie. But there are many fascinating facts about feathers that are not known by even the most experienced fly tier. Therefore, the purpose of my presentation is to try and provide an interesting and informative glimpse into the world of feathers to enhance the fly tier’s appreciation and use of them.
First of all, what are feathers? I’m sure everyone thinks they know. But are you aware that feathers are actually just elongated, highly specialized scales? Birds evolved from reptiles approximately 160 million years ago, and since that time the humble scales of the lizard-like ancestor of the bird (archaeopteryx, meaning “ancient feather”) have evolved into the staggering diversity and beauty that we now know as the plumage of modern birds. And these reptilian scales can still be found on the scaled feet and shanks of all modern birds attesting to their reptilian origin.
Second of all, feathers do not grow over the entire surface of the bird. I’m not referring, as an example, to the naked head of a turkey or vulture. Rather, feathers grow from the skin in discrete groupings known as feather tracts, which are called pterylae. And there are strips of unfeathered skin between these feather tracts, called apterylae, which typically are covered over and obscured by the neighboring feather tracts giving the appearance of full plumage coverage. This concept of feather tracts is important to the fly tier in that distinctly different feathers often come from the different tracts. As an example, dry fly hackle comes from the capital or head tract and the dorsal cervical tract, and sometimes from the dorsopelvic or back/saddle tract. True spade hackle, as in classic Coq de Leon feathers, are from the humeral tracts, which are a relatively small patch of feathers situated over the first and largest wing bone, the humerus. What we at Whiting Farms call our “Soft Hackle with Chickabou” pelt actually encompasses most of the feathers from the underneath side of the rooster, properly called the pectoral, sternal and medial abdominal tracts. The different feathers from within each of these distinct feather tracts have been experimented with by fly tiers and incorporated into a myriad of tying applications. And of course the fly tying function each type of feather provides to the tier is totally different and quite unrelated to the function the feathers provide to the bird.
Feathers, to the bird, are much more than just for insulation or for flight – feathers actually have quite a multiplicity of functions. Some of the major functions of feathers are:
Temperature Regulation
Tight to the body for heat dissipation, or fluffed out for insulation. Birds have small muscles associated with each feather which are able to raise or lower the feather angle relative to the skin for this insulation control.
Protection of the Skin
From abrasions, bird to bird encounters, and shade from sunlight to lessen UV light damage. Feathers provide a surprisingly durable protective covering.
Flight
The primary flight feathers (furthest out on wing) provide forward propulsion by sculling the air, pushing it behind the bird. While the secondary flight feathers (between the body and primaries) generate lift by creating an air foil.
Aerodynamic Contour
To streamline the body form to aid smooth passage through the air. And in penguins and other diving birds an exceptionally streamlined body form to facilitate ease of passage through water, plus provide a functional shell within which a layer of air is trapped which shields the bird from the frigid water.
Camouflage
Especially important in some ground nesting species.
Sexual Selection
Particularly evident in polygamous males attracting females to mate with. Can be a survival disadvantage, i.e., the huge peacock train; the size and beauty of which represents a natural selection equilibrium between maximum female attraction versus hampered male survival through breeding season.
Preen gland wick feathers
Dispenses preen gland oil, important to feather maintenance and water proofing. The preen gland is situated immediately in front of the tail and is the only skin gland on a bird’s body.
Powder feathers
Feathers which intentionally disintegrate to a talc-like powder to provide feather to feather lubrication, electrostatic reduction and water proofing.
Ear opening cover feathers
Rigid, grill-like feathers which let sound waves in yet keep debris out.
Rictal bristles
Whisker-like tactile feathers surrounding the beak on nighthawks and other on-the-wing insect catchers. Highly enervated sensors which trigger rapid beak opening and shutting upon encountering flying insects while the bird is in flight.
Narial bristles
Stiff, hair-like feathers which protect the openings to the nostrils. Particularly important to owls which fly through tree branches at night.
Whisper feathers
Serrated leading edge of primary flight feathers on owls which modifies air turbulences along the leading edge of the wing for nearly silent flight within the audible range of the owl’s rodent prey.
Besides having a multiplicity of functions, feathers also have highly specialized and specific growth patterns, both on an individual feather basis and over the life time of a bird, which address the changing functional needs of the bird through time.
First, feathers do not grow as hair does, which is characterized by a continuous extrusion of a relatively constant hair form. Feathers are also extruded by a follicle in the skin like hair, but they are fundamentally much more complex in structure, having a distinct tip, middle and base, often with radical differences between each of these parts (i.e., a peacock tail plume). And unlike hair, feather formation continues only until completion, then ceases, until the feather is lost or molted and an entirely new feather is generated.
My theory of what is happening at the genetic control level to create the long, consistent dry fly saddle hackle Whiting Farms is known for is that the follicle is stuck in “tip” mode and doesn’t ever progress to the feather “middle” mode, and so like a broken record or a computer loop, continues on churning out a continuous tip. I think this explanation is substantiated by the fact the saddle feathers on our dry fly roosters never “prime” or come to completion, but instead never cease growing or are even molted. We have selected for and “fixed” an aberrant trait for the benefit of fly tiers which provides no real benefit to the rooster yet surely has considerable metabolic and nutritional costs to them. The modern, genetic dry fly roosters could even arguably be viewed as just a life support system for follicles which extrude fly tying feathers, not unlike sheep and wool.
Another very important yet little appreciated fact is that each individual feather follicle has the potential to grow several, often radically different types of feathers, depending on the bird’s life stage and/or the season. A single feather follicle can initially generate the baby chick’s natal down, which is pushed out by the juvenile plumage, followed by the first basic plumage, which is succeeded by the second basic or alternate plumage often called the “nuptial plumage”. Dry fly hackle feathers are the male form of the latter plumage type. An example of seasonal feather variation is the ptarmigan’s plumage color; snow white for winter camouflage and mottled brown for summer, very different feather colors out of the very same follicles. Although there are many species specific variations to plumage types, this is generally the format and demonstrates the multipotential abilities of the humble feather follicle. Certainly feathers represent an awesome evolutionary accomplishment when compared to the modest reptilian scales of their origin.
Man over the last several thousand years has developed a myriad of breeds and varieties within the animals he’s domesticated. He has done so largely by identifying, isolating, stabilizing and perpetuating novel mutations which have arisen in these domestic species over time. Breeds and varieties therefore can be viewed as just stabilized conglomerations of various mutations. In addition, multigenic characteristics which present normal, bell-curve distributions, such as body weight, have also been intentionally selected towards extremes in some breeds (i.e., Great Danes to Chihuahuas). The incredible diversity amongst dog breeds is probably the best example of the genetic plasticity of our domesticated animals.
Plumage colors and patterns amongst the breeds and varieties of domestic chickens are also classic examples of such utilization of mutations. The fly tier then makes use of these novel colors and patterns to create flies to imitate the insects which attract fish. The genetic control of these colors and patterns is a fascinating study in and of itself and is, in some cases, quite surprising. Take for example the well known fly tying feather pattern of “grizzly”. Have you ever wondered how a chicken was induced to grow plumage of regularly alternating bars of black and white? It was a mutation which arose whose mode of action is akin to an auto immune effect whereby the pigment generating cells within the feather follicle (melanocytes for black and pheomelanocytes for browns) are periodically wiped out. During the pigment cells’ regeneration time the growing feather is devoid of pigment – resulting in the white section of the grizzly. After the pigment cells regenerate, but before they are wiped out again, the black portion of the grizzly pattern is created in the growing feather. From this mode of action it can be understood that a grizzly is actually a black chicken whose pigment deposition is regularly interrupted rather than a white chicken with periodic bars of black pigment added to it. This example of grizzly illustrates a fundamental mechanism of plumage colors and patterns – that colors and patterns are created by the extraction or inhibition of pigments, not by the addition of them. It is an essentially negative control system.
Another interesting example of this negative control system, which is also of importance to the fly tier, is the color mutation of blue dun. There are at least 6 genetic ways to create dun, but the best known and most common is the incompletely dominant gene “Bl”. This gene’s mode of action is to markedly reduce the quantity or concentration of pigment the melanocytes and pheomelanocytes generate as the feather is formed within the follicle. The Bl gene, or “blue gene” as it is sometimes called, is incompletely dominant, meaning it does not have its full effect unless it has a double dose of the gene; Bl Bl. With a double dose, and so its full effect, the chicken is nearly white or white with some splashes of color – Bl Bl, referred to as homozygous dominant. When it’s in the homozygous recessive form, bl bl, there is no effect and the chicken is black; no pigment inhibition is occurring. With a mixture of dominant and recessive, Bl bl – referred to as heterozygous – there is a partial pigment inhibitory effect and the black is reduced to a blue or gray color. One limitation of this incomplete dominant mode of gene action is that when two blue dun birds are mated together they will not “breed true” and give only more blue duns. Rather, their offspring will only result in a ratio of ½ blue, ¼ black and ¼ white. Only black mated with white generates 100% blues (bl bl x Bl Bl gives only Bl bl).
One of the most astonishing facts about plumage colors and patterns is that their enormous variety is solely the result of the action and inter-action of only two simple pigments: melanin for the blacks and grays and pheomelanin for the browns, buffs and creams. The modification of these pigments (i.e., dilution, as in dun), and their placement within the feather (i.e., barring, as in grizzly), together and separately, are capable of generating the fabulous diversity of colors and patterns within the bird world. The only other pigment capable of being generated in feathers is green, and that ability is limited solely to some parrot-like families of birds.
The iridescence of feathers, as in peacock herl, is not actually a product of pigment primarily. Rather, our perception of iridescence results from the refraction out, through an over coating on feathers, known at the cuticle, of limited bands of light wavelengths giving the perception of brilliant color. Prove this to yourself by holding a Peacock “eye” up to a sunny window and viewing the color of the feather with the sunlight shining through it. The feathers will not be iridescent at all, but rather a dull brown- its true structural color. This experiment demonstrates the difference between transmitted light (passing through the feather) and refracted light (reflecting off of the feather). This refraction of light is also why the brilliant iridescence of a hummingbird seems to shift color as the relationship between the sun, bird and viewer changes with any movement. The wavelengths of refracted light received by the viewer is what’s shifting, not the actual color of the hummingbird. Plumage is truly one of the wonders of the world.
If you are interested in greater depth and breadth of information on feathers, genetics and hackle production, may I suggest a recently (1997) published book Rare and Unusual Fly Tying Materials: A Natural History, Volume II – Birds and Mammals by Paul Schmookler and Ingrid Sils.
Within this photographically beautiful, large format book is a 50 page chapter on these subjects written by myself which I hope would satisfy any fly tier’s curiosity on hackle and feathers in general.
