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Re: Skin color of birds
My minor note to add to Mssr Alan's response is to mention the ocurance
of pterylosis, or, the patterns of skin that bears feathers (pteryla)
and areas that do not bear feathers at all (apteria) on birds.
In the Manual of Ornithology, Proctor and Lynch, it mentions that these
patterns of feather growth and non-growth of the skin change per species
of bird, so that skin that grows or does not grow feathers on the bodies
of these animals is an inheritable trait and species-distinct. (Thus
the PATERN of 'proto-feather' growth on an animal could be distinct from
flight capabilities entirely.)
The surface pattern of this skin, with 'pores' for the feather growth
from the skin vs 'pore-less' skin, would show a texture change at least
between the types of skin, if not a pigmented change of the skin.
In looking at the scaleless, featherless skin of some extant condors,
chickens, parrots, and turkeys, much of the exposed, nonscaled
skin seems to share some of the same textural qualities of human
skin exposed for long periods to sun- the texture is thicker, heavily
lined, shiny, and the surfaces that must be flexible (such as the skin
on the insides of throats or around the eye in parrots) is very thin,
VERY flexible, and nearly transluscent.
To find simular non-scaled skin on extant reptiles you have to look at
delicate surfaces such as eyelids or display structures such as throat
dewlaps (hanging or inflateable).
Most non-pigmented ornamentation that occurs with the skin of these
birds (wattles etc) is in the heavier-type skin and is textural
rather than pigmented.
The change from the scaled textural skin to feathered and
non-feathered unpatterned skin had to have happened between
reptile and bird in dinosauria. Since scales and scutes have
been shown to be present in dinosauria as well as featheres,
where would be the first real evidence of this softer, unscaled
skin surface that was ALSO introduced at the same time as feathers?
> Alan Brush wrote:
> In extant birds, the portion of the skin that bears feathers (e.g.
> most of the body) is usually unpigmented or slightly yellow in color.
> There are some exceptions, among them some chicken mutants pigmented
> by melanin. The skin does not generally reflect the colors of the
> feathers. However, the feathers do provide protection from the sun.
> The skin generally on the body is relatively soft and very loosely
> attached. That is why birds are so easy to skin. The skin contains
> numerous types of sensory nerve endings. There is also a set of
> specialized muscle that allow for the movement of the feathers in the
> follicle. The posture of the feathers can play a role in
> theromoregulation. Birds have no sweat gland in the skin.
> In the unfeathered portions such as the foot, the face and head the
> skin may be pigmented or display structural colors (i.e. blue,
> iridescent, etc). There are various additional structures such as
> wattles, comb, etc that are colored as well. These have all sorts of
> functions, may be under hormonal regulation and are actually rather
> complex structures.
> The color patterns of the feathers are independent of the underlying
> Hope this helps
> Alan H. Brush
> M.J. Spring Brush
> 92 High St.
> Mystic, CT 06355
Flying Goat Graphics
(Society of Vertebrate Paleontology member)