Chapter 4 - Feathers Flashcards

1
Q

Functions of feathers

A

. Insulation for regulation of body temperature.
* Aerodynamic power for flight.
* Colors for communication and camouflage.
* Modified feathers may also used for swimming,
sound production, hearing, protection, water
repellency, tactile sensation, etc.

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2
Q

Structure of feathers

A

Feathers are made of B-keratin, which is a
fibrous protein polymer with strong
mechanical properties.
* The same protein, B-keratin, is also found
in the beaks, claws, and leg scales of
birds.

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3
Q

Structure of Pennaceous Feathers

A

The vane consists of barbs, which are parallel,
lateral branches of the rachis.
* Each barb consists of a main ramus, which has
many smaller structures, barbules, projecting
from both the proximal and distal surfaces of the
ramus.
* Barbules that project from the proximal surface
of the ramus have a ridge for locking. Barbules
that project from the distal surface of the ramus
have hooks, also known as barbicels.
The hooked barbules from the distal surface of
one barb will hook around the barbules from the
proximal surface of the adjacent barb.
* In this way, the barbs and barbules interlock, like
Velcro, to form the flat but flexible structure of a
pennaceous vane.

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4
Q

Modifications of Vane Structure

A

In waxwings, the barbs near the distal ends of
some feathers are fused into a wax-like structure
that provides bright coloration

In the Desert Sandgrouse, the
barbules are coiled in a way that
allows them to hold on to extra
water. This species transports
water to its nestlings by dipping its
belly in water and then carrying it
to the nest.

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5
Q

Modifications of Vane Structure In Cormorants and anhingas

A

In cormorants and anhingas, the loss of
barbicels actually makes the feathers absorb
more water, which helps to reduce buoyancy
during diving. However, these feathers require a
long air drying time.

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6
Q

Modifications of Vane Structure in rails and ducks

A

the barbs are large and
close together, and the barbicels are extra
long and curved. This causes the feathers
to be more water-repellent.
King Rail

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7
Q

Structure of Plumulaceous Feathers

A

The loose vanes of
plumulaceous feathers
do have barbs, and
those barbs have
barbules. However, the
barbules do not have
hooks, so they do not
interlock with barbules
on adjacent barbs.

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8
Q

Aftershaft

A

The contour, or body,
feathers of some bird
have a secondary
structure called an
aftershaft. An aftershaft
consist of another
rachis and vane
attached to the same
calamus.
* Main function is to
enhance insulation.

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9
Q

Flight Feathers

A

The flight feathers include feathers of the wings (remiges
– provided lift and thrust) and feathers of the tail
(rectrices – used for steering and braking).
* Long, pennaceous feathers designed for aerodynamic
forces during flight.
* Coverts cover the bases of these feathers.
Undertail Coverts

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10
Q

Remiges

A

divided into primaries and
secondaries. The primaries attach to the bones
of the hand, while the secondaries attach to the
ulna.
The leading edges of remiges are narrow than
the trailing edges; this limits vibrations of the
leading edge.
* This effect is more pronounced on primaries
than on secondaries.

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11
Q

Owl Flight feathers

A

The rectrices on the feathers of owls have a
modified leading edge. The distal barbs on the
leading edge have very long tips called
pennulae. These create a fuzzy edge on the
surface of the vane that reduces air turbulence
and vibration while in flight. This allows the owls
to have a more silent flight.

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12
Q

American Woodcock flight feathers

A

Male American Woodcocks due a ritual display
flight to attract mates. Males will spiral upward
into the sky while his wings make twittering
sound produced by air passing through three
narrow outer primaries.

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13
Q

Duck Flight feathers

A

In many ducks, the secondaries form a
prominent colorful patch called the
speculum.
In the Mandarin Duck, the secondaries are
erected during courtship displays.

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14
Q

What are the rectrices attached to

A

The rectrices are attached to the
pygostyle.

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15
Q

Tail feathers can be modified in various
ways.

A

Woodpeckers, Wilsons Snipe, Courtship

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16
Q

Contour feathers

A
  • These are body feathers. They help to define the
    outline, or contour, of the bird.
  • Often pennaceous distally and plumulaceous
    proximally (toward the calamus).
  • Help to streamline the
    bird for flight.
  • May play a major role
    in waterproofing.
17
Q

Down feathers

A

Short, extremely plumulaceous feathers that has a
weak central rachis (or lacks a rachis altogether).
* Adult (Definitive) Down provides a layer of insulation
under the contour feathers and aids in repelling
water.
* Natal Down, found in hatchlings, serves as the initial
plumage before it is replaced.

18
Q

Semiplumes

A
  • Similar in shape to a contour feather, but
    completely plumulaceous.
  • Have a distinct rachis.
  • Lie underneath the contour feathers to fill gaps;
    also help to insulate.
  • May serve as courtship ornaments.
19
Q

Powder Down

A
  • Specialized feathers with barbs that disintegrate
    into a fine powder. Thought to aid in grooming
    and waterproofing.
  • The only feathers that grow continuously and
    are never molted.
  • Especially prominent in herons.
20
Q

Filoplumes

A
  • Long, hairlike feathers that
    monitor the positions of
    pennaceous feathers
    (especially the remiges and
    rectrices).
  • Consist of a rachis with a tuft
    of barbs near the tip.
  • Sensory corpuscles in the
    follicle of each filoplume detect
    fine movements of the shaft.
21
Q

Bristles

A
  • Specialized feathers that can have sensory or protective
    functions.
  • Consist of a stiff rachis with just a few basal barbs.
  • Eyelashes of ostriches, rheas, hornbills, and cuckoos are
    bristles.
  • Located around the mouths of nightjars, where they
    collect tactile information.
22
Q

Feather Coloration

A

Colors in feathers are due to pigments,
structure, or both.
* Pigments are organic compounds that
absorb the energy of certain wavelengths
of light and reemit the energy of other
wavelengths to produce the observed
colors.

23
Q

three major types of pigments

A
  1. Melanins produce grays, blacks, browns,
    and buffy colors.
  2. Carotenoids produce bright yellows,
    oranges, and reds (and some purples).
  3. Porphyrins produce reddish-brown colors
    and, in some African birds, olive-green and
    magenta.
24
Q

Melanins

A

Nearly all feathers have some melanin in them.
* Synthesized in melanocytes in the skin from the amino
acid tyrosine.
* The melanin is packaged into melanosomes, which are
then transferred into developing feathers.
* Pigmentation patterns with feathers are due to temporal
variations in the transfer or melanosomes.

25
Two Kinds of Melanin
Eumelanin (blacks and grays) and Pheomelanin (reddish- brown, buffy-tan, and rufous colors).
26
Melanins have multiple functions (other than imparting color)
1. Increase resistance to stress and wear. 2. Increase resistance to degradation by feather-eating bacteria. Some bacteria secrete an enzyme that breaks down b- keratin. Increased levels of melanin reduce this damage. 3. Absorb radiant energy. This may help with thermoregulation.
27
Carotenoids
* Originally produced by plants and derived by diet. * Thirty-nine different carotenoid molecules have been identified in feathers. * The reds, oranges and yellows of parrots come from a different class of pigments known as psittacofulvins (not derived from diet).
28
Porphyrins
Ring-shaped molecules similar to hemoglobin and chlorophyll in structure. * Causes magenta and bright olive-green coloration in turacos.
29
Structural Colors
* Includes blues, some reds, some greens, and iridescence. * Color is produced when light waves bounce off the interfaces of nanometer- scale structures in the feather.
30
Three different classes of structural feathers
1. White - Random reflectance of all visible wavelengths produces white when light scatters off cellular air bubbles. For example, the Rock Ptarmigan is white due to extra large air bubbles in the barbules, which magnifies the amount of light reflected. 2. Iridescence - Reflectance of wavelengths from layers or arrays of melanosomes in the barbules. This produces iridescence (a change in hue dependent upon the angle of illumination or observation). The color produced depends on the size of the melanosomes and how they are arranged. 3. Non-iridescent Colors – Produced by reflectance of wavelengths off air bubbles within cells of the rami of the feather barbs. The same wavelengths are backscattered regardless of the angle of incidence or observation. Smaller bubbles produce bluer colors, while larger bubbles produce greener colors
31
Ultraviolet Colors
The blue and violet colors of birds are often also rich in ultraviolet (UV) reflectance. * Humans cannot see UV wavelengths, but most birds can. * All avian families exhibit this trait.
32
The Plumage
* The entire plumage consists of thousands of feathers. * Tundra Swan = 25,000 feathers * Most Songbirds = 2,000 – 4,000 feathers * The feathers weigh 15-20% of the total body mass.
33
Pterylae vs Apteria
he pterylae include numerous feather placodes which each develop into a feather follicle. Each follicle grows a series of feathers, which are replaced over time by periodic molts. Apteria are spaces between pterylae which lack contour feathers or which lack feathers entirely.
34
Feather Care
Birds preen their feathers with their beaks and toes to maintain their pennaceous feather vanes and to remove parasites (mites, lice, bacteria, etc.) * Birds also apply a waxy secretion from the uropygial gland (preen gland), which is located on the rump. This preserves feather moistness and flexibility and helps to waterproof the feathers. * Some birds have miniature combs on the inner margins of their middle claws. * Allopreening
35
Molt
Alternate plumage throughout life
36
Sexual Dimorphism
Many species are sexually dimorphic