Lab 3 – Topography and Feathers
What to know: Underlined terms, terms on terminology page, and
information from feather pwrpt.
PART I. TOPOGRAPHY
Any description of external characteristics of birds generally uses some specialized
terminology for particular regions, feathers, etc. Knowledge of this terminology is especially
important for identification whether with a field guide or a dichotomous key.
Familiarize yourself with the topographic features illustrated in your field guide and the
figures with those discussed below. Locate the features on several specimens to see how they
vary among species.
Figure 1. General Topography,
also see your field guide
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BILL. See Figure 2. The culmen is the uppermost, central ridge of the upper mandible.
Tomia (sing. = tomium) are the cutting edges of both mandibles. The nostrils generally open
into a depression on the bill. In pigeons and doves there is a soft swelling over the nostril called
the operculum. On the ventral side, the lower mandible has a posterior projection on each side
called the mandibular ramus. The lowermost ridge of the lower mandible is the gonys. The
gape is the angle where the mandibles come together (field guides sometimes describe the
color of the gape).
Figure 2. Head Topography
Diagram from:
Proctor, N., and Lynch, P. (1993).
HEAD. See Figures 1 and 2. The
Manual of ornithology: Avian structure
and function. New Haven: Yale
University Press.
HEAD. See Figures 1 and 2. The back portion of the head progresses from the crown
to the nape. The eye stripe is also called the superciliary line. The auriculars cover the ear and
so are sometimes termed the "ear patch". The chin is the feathered area between the lower
mandible and the throat.
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TRUNK. See Figure 1. The areas here often are used in descriptions of birds. Most
important are back, rump, abdomen or belly, side, flank, and breast (upper breast referred to as
chest).
WINGS. See Figure 3. Locate the features of the wings on the spread wings. Do not
try to open folded wings. The flight feathers or remiges have long, stiff quills and are of two
groups. The primaries attach to the manus and are numbered from the innermost one outward.
The secondaries attach to the ulna and are numbered from the outside in. On the dorsal
surface a group of feathers arise from the shoulder and adjacent brachium; these are scapulars
(Fig. 1). In a comparable position on the ventral side in the "armpit" are the axillars. The alula,
arises from the thumb (or digit II). Overlying the alula and the remiges on the dorsal and ventral
surfaces are smaller feathers called coverts. They are named depending on location, size, and
what they cover; they lie in overlapping rows along the wing.
TAIL. See Figure 1. The paired tail feathers or rectrices are the flight feathers of the
tail. They are covered by tail coverts similar to the wing coverts but only the under tail coverts
are differentiated. The upper tail coverts are indistinguishable from the rump.
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Figure 3. Wing
Topography
Diagram from:
Proctor, N., and Lynch, P.
(1993). Manual of
ornithology: Avian
structure and function.
New Haven: Yale
University Press.
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PART II. FEATHER STRUCTURE, TYPES, AND DISTRIBUTION
General feather structure. See Figure 4 and 5. Examine a typical feather from those
available. The shaft (calamus + rachis) or quill forms the mid-rib. The lower part of the shaft
below the vanes is the calamus. The rachis is the part supporting the vanes. At the base of the
shaft is the inferior umbilicus, an opening through which blood and nutrients flowed to the
feather during development. When the feather is fully developed, the opening is closed by a
horny plate. Near the base of the vane is another small opening, the superior umbilicus. It, too,
is a remnant of feather growth. The developing vane emerged through that opening.
In some species there is an aftershaft or afterfeather, a shaft (sometimes with vanes)
which appears near the superior umbilicus. It is best seen in the abdominal feathers of grouse.
The body of the feather consists of two vanes. The vane overlapping the next outer feather is
termed the outer vane and is narrower. The vanes are pennaceous and more rigid distally.
Proximally, they are often downy.
The vanes are a series of barbs extending laterally from the shaft. Each barb, in turn, is
made of a central ramus and two laterally projecting rows of barbules. The distal barbules, ones
on the dorsal side of the ramus, have hooklets that project distally and hook over the proximal
barbules from the next higher (distal) barb. This hooking mechanism is enhanced by flanges on
the proximal barbules. Pull down gently on the vane and separate the barbs. The barbules can
be seen with the naked eye. Pull the feather between two fingers to rehook the barbules. This
is the same movement as done with the bill as a bird preens.
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Figure 4. Feather Structure
TYPES OF FEATHERS. There are five principal types of feathers (Fig. 5):
(1) Contour feathers give shape and a smooth protective surface to the body and are
used for flight in the wings and tail. Contour feathers vary considerably in shape, size, and
texture over the body. This is the typical feather just examined.
(2) Down feathers are small, with poorly developed shafts and no interlocking barbules.
They are the principal feather type in young birds and are important as insulation in most birds.
They lie under the contour feathers. Powder down is a specialized type of down best developed
in herons. They are yellowish and grow in two patches on the breast. The other feathers are
dusted with the powder produced by these feathers.
(3) Semiplumes are intermediate between contour feathers and down feathers. They
have a large rachis but no hooks.
(4) Filoplumes are hair-like feathers that can be seen after all other feathers have been
plucked from a bird. There are barbs only near the tips. They are thought to provide a sense of
touch in the plumage, much like the small hairs on human skin do.
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(5) Bristles occur in some birds around the eyes or in the rictal region (rictal bristles).
They have a stiff, tapered shaft, occasionally with a few barbs. Rictal bristles often are
considered to serve as an "insect scoop" for birds that feed on the wing. They more likely have
a sensory function.
Figure 5. Feather Types
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FEATHER TRACTS. In most birds, contour feathers lie in tracts on the body. The
spaces between the tracts, which are without feathers are called apteria. Down feathers,
filoplumes, etc., may lie in the apteria. There are nine major tracts: capital, spinal, caudal,
femoral, crural, ventral, humeral, and alar.
FEATHER COLOR. Coloration in feathers is chemical and due to pigments, structural
and due to physical properties of the feather, or both. Red, orange, yellow, black, gray, brown,
and some greens are chemical. White and iridescent colors are structural. Blue and some
greens are a combination of both. See Gill pages 94-100 for more information.
MODIFICATIONS OF CONTOUR FEATHERS. Some contour feathers are modified in
various ways in different species. Examine the following:
(1) Narrow, stiff outer primaries of the American Woodcock. These produce sound in
flight; used in courtship display and territorial defense.
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(2) Waxy tips of secondaries of Cedar Waxwings are caused by a fusion of barbs. The
function is unknown.
(3) Stiffened rectrices of woodpeckers and the Brown Creeper. These serve as support
when perched on vertical surfaces.
(4) The nasal tufts of the crow.
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PART III. Terminology
We will encounter a wide diversity of terms. In an effort to speed your familiarity with
this terminology, the following synopsis is provided. In each case, an example of a bird
showing that characteristic is given.
Bill:
toothed (falcon)
notched (thrush)
lamellate (duck)
serrate (merganser)
Tail shape:
pointed (Sharp-tailed Grouse or
pheasant)
square (flycatcher)
forked (Barn Swallow)
rounded (Blue Jay)
graduated (cuckoo)
Toe membranes and appendages:
palmate (duck)
semipalmate (sandpipers)
totipalmate (cormorant)
lobate (grebes, coot)
Wing characters:
rounded (owls, buteos)
broad (owls, buteo)
pointed (terns)
narrow (tern)
long (terns, gulls)
short (grebe)
Toe arrangement:
anisodactyl (songbird)
zygodactyl (woodpecker, osprey)
heterodactyl (only trogons – do not
need to know)
pamprodactyl (swift)
syndactyl (kingfisher)
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