Download Contour feathers

Knowledge is the antidote to fear.
- Ralph Waldo Emerson
CHAPTER 21 BIRDS
MS.COX
Introduction
 Birds are grouped into a class called Aves.
 Because they have unique adaptations for
flight.
 It is believed that birds first evolved from the
archosaur of reptiles.
 Birds have the following things in common
with reptiles: one occipital condyle, one ear
ossicle, the lower jaw structure, nucleated red
blood cells, nesting behavior, and parental
care.
Introduction
 Birds however have some things that are
unique to them:
 Feathers, wings, endothermy, modified
vertebral column, light bones, horny bill
without teeth.
Fossil Records
 Evidence from Archaeopteryx
 Shows that these ancient reptiles may have
climbed up trees with claws and then glided a
flew short distances.
 Another idea is that birds ran or hopped
along the ground and then trapped prey with
their wings.
 There have been fossils found to show flight
and some that show flightless birds.
Ancient Birds
Fossil Remains
Today
 In the bird group there are
about 9,100 different
species, divided into 27
orders.
 See page 329, the table will
be on the test
Characteristics
 Feathers- also called plumage
 Function to: allow flight, help species recognize one
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another, mate attraction, endothermy, and
waterproofing.
Color of Feathers
May be due to pigments, reflected light, or
iridescence.
Feathers are keratinized
Contour feathers cover the body, wings, and tail.
Contour Feathers
 Structure of Contour Feathers
 1. Consist of a vane with its inner and outer webs,
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and a supportive shaft.
2. Feather barbs branch off the shaft.
3. Barbules branch off the barbs.
4. Barbules of adjacent barbs overlap one another.
The ends lock with the hook like hamuli (see picture
on next slide).
5. The interlocking of barbs keep contour feathers
firm and smooth.
Hamuli- Hook
Parts of
the Feather
Contour feathers give the bird its
characteristic smooth round shape.
They also give the bird its visual
coloring and provide a first level of
defense against physical objects,
sunlight, wind and rain. They are
very important.
Down feathers are smaller
and lack the barbules and
their accompanying hooklets
so they are not zipped
together and do not look as
neat. In fact they are soft
and fluffy. They provide
most of the insulation and
are so good at this that
mankind for many years
collected down feathers from
various birds to put into
sleeping bags and jackets to
help keep us warm.
Semiplumes are
half-way between a
contour feather
and a down
feather. These
occur between the
contour feathers
and help to supply
insulation and a
certain amount of
form as well.
Filoplumes are
very small and
have only a very
few barbs at
their
tips. They are
believed to have
a sensory
function,
helping birds
keep their
feathers in
order.
Diversity of Feathers
Feather Maintenance
 Birds clean their feathers by preening (rubbing the
bill over the feathers, keeps the feathers smooth,
clean and in place.
 Secretions from the oil gland at the base of the tail
are spread all over the body which help keep the
plumage water repellent and supple. This keeps the
bill and legs from chafing.
 Anting- many songbirds pick up ants with their bill
and rub them all over the feathers. The formic acid
that ants secrete is toxic to feather mites. So birds
use them to keep parasites away.
An Egret Preening
Color of Feathers
 Feather pigments are deposited during
feather formation most colors in a bird’s
plumage.
 Other colors arise from irregularities on the
surface of the feather that diffract white light.
 An example of iridescence is the perception
of interchanging colors on the neck and back
of hummingbirds.
Iridescent feathers change color
when seen from different angles
or in different light conditions.
The tips of the feathers have
tiny platelets that either allow
light to pass through or reflect
it. The result is an amazing
light show that has the viewer
seeing a lustrous rainbow of
colors.
The peacock is the most famous of
birds with iridescent feathers,
but many of the more drab colored
birds also display iridescence.
The black parts of magpies and
starlings sometimes appears to be
blue or green.
Molting
 Molting- the periodic shedding of feathers
 The timing of molt periods varies.
 Flight feather are frequently lost in a
particular sequence so that birds are not
wholly deprived of flight during molt periods.
 However some birds like ducks can not fly
during molt periods and have to hide in thick
march grass until the molt is completed.
Duck Molting- this takes a couple of weeks
Other birds molting
Birds Skeleton
 Characteristics:
 Lightweight, large bones have air spaces, other
bones are smaller in size.
 Like reptiles they have uncinate processes, that
strengthen the rib cage.
 The rear of the bird is adapted for running,
hopping, or perching.
 The neck is flexible
 The synsacrum and pygostyle support and
steady the pelvic region while walking, hopping,
and flying.
Elephant Bird
Skeleton
Skeleton Drawing
Key to worksheet
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1) Skull
2) Cervical Vertebrae
3) Humerus
4) Second digit
5) Metacarpals
6) Fourth digit
7) Third Digit
8) Radius
9) Ulna
10) Scapula
11) Synsacrum
12) Pygostyle
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13) Ischium
14) Ilium
15) Pubis
16) Pelvic girdle
17) Uncinate process
18) Femur
19) Halux
20) Digits
21) Tarsometatarsus
22) Tibiotarsus
23) Keeled sternum
24) Coracoid
25) Furcula (or wishbone)
The bones
While maintaining strength, most of the bones
are pneumatic, meaning they are hollow and
filled with air spaces connected to the
respiratory system.
 Skull
 The bones of the skull are generally fused providing
protection to the brain while being of light weight. A
light, toothless beak replaces the bony, heavy
toothed jaw of reptiles. Beaks, of course, can be
highly modified for different types of food and
feeding behavior Note the large orbits, as sight is
an important sensory mechanism for birds.
Neck
 The necks of birds are very important for body
maintenance and eyesight. Modification for flight
has rendered avian forelimbs almost useless for any
task other than flight. To make up for this lack of
forelimb dexterity, the beak is used for many tasks
such as preening feathers. To access hard-to-reach
feathers on the back and tail birds require a flexible
neck. Furthermore, as birds have immobile eyes,
head movement and flexibility is required to focus
on objects at various distances.
Thorax and Sternum
 Overlying flaps projecting off the ribs called
uncinate processes help to stiffen the rib cage
so it will not collapse during the powerful
strokes required for flight. The sternum is the
highly modified breastbone. In flying and
swimming birds the keel is enlarged for flight
muscle attachment. Flightless birds such as
Ostriches have a sternum without a keel.
Pectoral Girdle
 The pectoral girdle is made up of the
sternum, clavicle, coracoid and scapula. The
clavicles come together to form the furcula,
or "wishbone". The furcula provides a flexible
attachment site for the breast muscles and
along with the coracoids act as struts that
resist pressure created by the wing stroke
during flight. Flight muscles running from the
sternum to the relatively short and stiff
humerus elevate and depress the wing.
Pelvic Girdle
 There is an extensive fusion of bones of the
pelvic region to provide stiff support for the
legs in order to deal with the stress of take-off
and landing. The synsacrum is a fusion of the
pelvic and 6 caudal (tail) vertebrae. At the end
of the spinal column is the pygostyle, a fusion
of the final few caudal vertebrae. The
pygostyle supports the tail feathers and
musculature.
Wing
 The avian wing contains the usual arm bones of
reptiles and mammals, but in a highly modified
form. The humerus is rather short compared to the
total length of the wing, as it must withstand the
pulling of the flight muscles. The radius and ulna
form the support for the mid-wing. The outer wing
or "hand" bones are highly fused for strength and
feather support. The first digit or pollex supports the
alula, a small feather used to control air flow around
the wing.
Leg and Foot
 The upper leg is composed of a fairly
standard femur, but the lower leg and foot
are highly modified by fusion of bones. Of
course, between the femur and the fibula and
tibiotarsus is the knee, whose location in
birds is often confused. The tarsometatarsus
is an extended fusion of the foot bones. This
lengthening adds extra leverage for running,
landing and take-off.
Foot
Types
SONG BIRDS or PERCHING BIRDS (warblers, thrushes, wrens,
etc.) have independent, flexible toes, with one pointing backwards,
ideal for grasping perches. Why don't perching birds fall out of trees
when they sleep? When perching birds sit, a tendon on the backside
of the ankle automatically flexes locking their toes around the
branch. With feet locked, sleeping birds don't fall. As the bird stands
up its feet release.
WOODPECKERS have two toes pointing
forwards and two backwards; for climbing
up, down, and sideways on tree trunks.
WATER BIRDS such as ducks have webbing
between their toes for swimming. GULLS
also have feet similar to these so they
don't sink while walking in the soft sand
or mud near the water's edge.
WADING BIRDS. The long toes of herons,
which spreads the bird's weight over a
large surface area, facilitates walking
on soft surfaces near the water's edge
(where wading birds like to eat).
RAPTORS such as hawks, eagles, and owls
use large claws (called talons) to
capture, kill, and carry prey with their
feet.
Pheasants and chickens use
their strong feet to scratch
the dirt and leaf litter to
uncover seeds and insects.
Strong-legged flightless birds, like the
Cassowary, protect themselves by kicking with
their powerful feet and sharp claws.
Skeleton Continued
 Bird flight alternates between gliding and
flapping flight.
 It requires a lot of energy also called ATP.
 The keel on the sternum is enlarged for the
attachment of the strong pectoral flight
muscles.
 Airfoil design allows or creates lift.
Types of Nests
 Ground nests were probably the first
nests made by birds. They are usually
just "scrapes' on the ground forming a
depression. Birds shape these type of
nests by rotating their abdomen in the
same place many times. Shorebirds
typically employ this type of nest. The
picture to the left is a ground nest of a
Killdeer. An interesting note about
shorebirds is that they almost always
lay four eggs.
Types of Nests
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Platform nests were
probably the first
elevated nests. Platforms
eliminate risk from most
ground predators. These
type of nests, built by
herons, cormorants,
eagles and osprey (right)
are very simple in
structure. Essentially
they are a collection of
loosely gathered sticks
and twigs with a slight
depression to hold the
eggs. Platforms can get
quite large because some
birds use the same
platform year after year
adding more material to
the existing nest each
year.
Types of Nests
 Insulated cavity-nests shelter eggs from
cooling winds and allow the parent's body
heat to warm the eggs more efficiently.
Many species use cavities as their nesting
location, including woodpeckers, titmice,
chickadees, owls, and bluebirds just to name
a few. Nest cavities also serve as a valuable
roosting spot, giving birds a place to "hideout" during inclement weather. Cavitynesting species have a keystone role in the
environment because many other types of
animals use old cavities for their homes. For
example, southern flying squirrels often use
old red-cockaded woodpecker cavities for
their nesting location.
Types of Nests
 Cupped nests are the
most recognizable, most
solid, and most complex
of all of the nest types.
Most songbirds build
cupped nests in a variety
of shapes and sizes. The
pictures below illustrate
several types of cupped
nests and the species that
build them.
Digestion
 Birds depend heavily on their digestive systems
to remain nourished and healthy.
 Many birds can starve in hours if deprived of
food, therefore, their digestive system is faster
and more efficient than those of other
vertebrate groups.
 Digestion in birds involves a lot of organs, each
performing a specific function. It begins with
entry of food via the beak and ends with waste
exiting at the vent. Food is broken down and
absorbed for use along the way.
Digestion
 The discussion of avian digestion begins with
the mouth.
 1. Bird beaks or bills replace the lips and
teeth of mammals and vary in shape, size,
length and function according to the type of
diet consumed. Seed-crackers such as finches
have a short conical beak, while birds of prey
such as hawks have a powerful hooked beak
for tearing flesh
Digestion
 2. The tongue of birds, just as the
beak, is adapted to the type of food
the bird consumes.
 Woodpeckers have a long narrow
tongue which functions as a spear,
allowing them to extract insects from
holes they drill in dead wood.
 Birds of prey and finches have short,
thick, fleshy tongues which allow
them to manipulate their food.
 Fowl and pelicans have tongues
which allow the food to be easily
shoved to the back of the mouth
for swallowing.
 A birds mouth is relatively
unimportant in eating and
digesting food in comparison
with, for example, the
mammalian mouth. However,
most birds do have salivary glands
and the beak and tongue do help
birds manipulate food for
swallowing.
Digestion
. After leaving the mouth, food
passes through the esophagus on its
way to the stomach (in birds called
the proventriculus). Many species of
birds have an enlarged area of the
esophagus known as a crop. The crop
is well developed in most species and
serves as a temporary storage
location for food.
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4. Crop shapes from various species of
birds
 The crop also allows food to be
softened before it enters the
stomach.
 Pigeons and doves produce "crop
milk" that they feed to their young for
the first two weeks after hatching.
Other species, such as ospreys, will
regurgitate food that has been stored
and softened in their crops and feed it
to their young.
Digestion
 5. Birds have a two part stomach, a
glandular portion known as the
proventriculus and a muscular
portion known as the gizzard.
Hydrochloric acid, mucus and a
digestive enzyme, pepsin, are
secreted by specialized cells in the
proventriculus and starts the process
of breaking down the structure of the
food material.
 The food then passes to the second
part of the stomach, the gizzard. The
gizzard performs the same function
as mammalian teeth, grinding and
disassembling the food, making it
easier for the digestive enzymes to
break down the food. In most birds
the gizzard contains sand grains or
small rocks to aid the grinding
process.
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The small intestine is where food is
digested and absorbed. The small
intestine varies in length and
structure depending on the diet of the
species. Carnivorous birds tend to
have shorter, less complex small
intestines. Herbivorous birds have
longer, more developed small
intestines. Enzymes, produced in the
pancreas, break down proteins and
fats in the small intestine. Nutrients
are then absorbed through the
intestinal membranes and into the
bloodstream.
The avian large intestine is
reduced to a short, featureless
connection between the small
intestine and the cloaca.
 8. The cloaca is the final
holding area for the waste
products of digestion until they
are voided through the
 9. vent
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Bird Beaks
 Did you ever wonder why there are so many
types of bird beaks or bills?
 The most important function of a bird bill is
feeding, and it is shaped according to what a bird
eats. The bill is one of the characteristics used to
identify birds.
 You can learn about bird behavior by looking at
the bill and thinking about what it eats. Then you
may think about where it lives, and so on.
Following are some common bill shapes and a
description of the food they are especially
adapted to eat.
Cone Shaped Bill
 A cone shaped bill is
found in many birds
such as finches and
grosbeaks. It is a strong
beak used for cracking
seeds.
Slender Pointed Beaks
 Thin, slender, pointed
beaks are found mainly in
insect eaters. They are
used to pick insects off
leaves, twigs, and bark.
This warbler is a good
example. Woodpeckers
have strong beaks which
taper to the tip, forming a
chisel for pecking holes in
trees for food or nests.
Most feed on insects which
live under the bark.
Beaks
 Hummingbirds have long,
tubular bills that resemble
straws, which they use to sip
nectar from flowers
Mergansers, specialized for
eating fish, have sharp toothlike structures on the edge of
the bill to hold fish tightly.
Hawks, owls, and other birds of prey
which catch and kill live prey have
sharp, "hooked" beaks. These are used to
bite the skull or neck and also to tear
the body into pieces small enough to
swallow.
The edges of a Mallard's bill
are fringed to strain plants,
seeds, and small animals from
mud and water.
Beaks which are flat and wide at the base are
found in birds which catch insects in flight,
such as flycatchers. These birds also often have
whiskers at the corners of the mouth, which
effectively widens the mouth opening, allowing
more effective capture of prey.
Respiration
 Avian Respiration
 The avian respiratory system delivers oxygen
from the air to the tissues and also removes
carbon dioxide. The avian respiratory system is
different from that of other vertebrates, with
birds having relatively small lungs plus air sacs
that play an important role in respiration (but are
not directly involved in the exchange of gases).
The air sacs permit a unidirectional flow of air
through the lungs.
 Unidirectional flow means that air moving
through bird lungs is largely 'fresh' air and
has a higher oxygen content. Therefore, in
bird lungs, more oxygen is available to
diffuse into the blood. In contrast, air flow
is "bi-directional" 䁩n mammals, moving
back and forth into and out of the
lungs. As a result, air coming into a
mammal's lungs is mixed with 'old' air (air
that has been in the lungs for a while) and
this 'mixed air' has less oxygen.
Respiration
 The air sacs can be divided into anterior sacs
and posterior sacs. Air sacs have very thin
walls with few blood vessels. So, they do not
play a direct role in gas exchange. Rather,
they act as a 'bellows' to ventilate the lungs.
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Respiration
 So, how does air flow through the
avian lungs and air sacs during
respiration?
 1 - On first inhalation, air flows
through the trachea & primarily into
the posterior (rear) air sacs
 2 - On first exhalation, air moves
from the posterior air sacs & into the
lungs
 3 - With the second inhalation, air
moves from the lungs & into the
anterior (front) air sacs
 4 - With the second exhalation, air
moves from the anterior air sacs back
into the trachea & out
 It takes two respiratory cycles to
move one "packet" of air completely
through the avian respiratory system
(see 1, 2, 3, and 4 above). The
advantage is that air, high in oxygen
content, always moves unidirectional
through the lungs.
Respiration
Migration
 Migration is the seasonal movement of animals
from one habitat to another. Animals migrate
between their wintering and breeding habitats.
Some creatures that you would recognize that
migrate are: whales, fish, butterflies, turtles, and
of course birds. Some animals travel incredible
distances on these annual journeys. The longest
migration of any known animal is that of the
Arctic Tern, which travels 15,000 miles from the
North Pole to the South Pole and back again
each year!
Migration
 Migrating birds follow established migratory
routes. Migration in North America is essentially
north-south along four major routes known as
"flyways:" Pacific, Central, Mississippi and
Atlantic. Many birds migrate between North and
South America and are referred to as Neotropical migrants (Neo = new + tropical). Most of
these birds migrate 500 miles non-stop over the
Gulf of Mexico. Other birds island hop down the
eastern coast of the U.S. (see maps
below). Upon arrival in southern wintering
grounds, birds have been described as nothing
more than "feathered skeletons" having
depleted much of their fat and muscle reserves.
Migration
 Why do birds Migrate?
 Seasonal cycles of climate or insect abundance attract
corresponding cycles of breeding, flocking, and migratory
relocation.
 Migration benefits are species or population specific and include
the need to escape inhospitable climates, probable starvation,
social dominance, shortage of nest/roost sites, or competition for
food.
 Another way to view the same ecological forces is that migrants
aggressively exploit temporarily available opportunities.
 Traveling to different habitats enables birds to find plenty of food
throughout the year. For example, in the winter, when food
sources are limited in northern areas, waterfowl such as geese fly
south to areas that have mild weather and abundant food.
Bird on
a
Mission
Migration
 How do birds navigate over such large tracts of land
and ocean?
 It has been demonstrated that birds rely on several
different cues – visual landmarks, geomagnetic field,
solar compass, skylight polarization pattern/stars, and
olfaction - for their orientation and navigation across vast
stretches of land.
 Schlicte and Schmidt-Koenig (1971) fitted well-trained
homing pigeons with frosted contact lenses that limited
image formation beyond 3 meters. The blind birds flew
over 170 km directly back to their lofts. Of course some
crashed into the loft and some missed the loft
altogether!
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Migration
Patterns
Migration
Brood Parasitism
 Birds are well known for their parental care,
patiently incubating their eggs and then bringing
food to their young until they are old enough to
look after themselves. However, certain birds,
known as "brood parasites," lay their eggs in the
nests of other birds and do not provide any
parental care for their own offspring. Care that
the "hosts" provide to the young parasites is care
denied to their own young. This often has a
detrimental effect on the reproductive success of
the hosts and may affect their population
numbers as well.
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 There are two types of brood
parasitism, non-obligate and
obligate. Non-obligate brood
parasites lay eggs in the nest of
cospecifics (i.e. same species) and
in their own nests. Examples
include several colonial nesting
species such as Bank Swallows or
African Weavers.
 Obligate brood parasites lay eggs in nests
of other species and have completely lost
the ability to construct nests and incubate
eggs. Examples include Brown-headed
Cowbirds and European Cuckoos. About
1% of all known bird species are obligate
brood parasites. Other obligate brood
parasites include: all African Honeyguides,
about half of the species of cuckoos, the
Black-headed Duck in South America,
Shiny Cowbirds, Screaming Cowbirds,
Bronzed Cowbirds, and Giant Cowbirds.
Brood Parasitism
Brood Parasitism
Brood Parasitism