Transcript Bird pwrpnt

BIRD NOTES
EXTERNAL STRUCTURE
AND MOVEMENT
• The covering of feathers on a bird is called the
plumage.
• Feathers have 2 primary functions that are
essential for flight.
– They form the flight surfaces that provide lift and aid in
steering.
– They prevent excessive heat loss.
EXTERNAL STRUCTURE
• Feathers are also important in courtship,
incubation, and water proofing.
• As feathers mature, their blood supply is cut off,
and the feathers become dead.
EXTERNAL STRUCTURE
• The most obvious feathers are contour feathers,
which cover the body, wings, and tail.
• These feathers consist of a vane and a supportive
shaft.
• Feather barbs branch off the shaft, and barbules
branch off the barbs.
• Barbules of adjacent barbs overlap one another.
• The ends of barbules lock together with hamuli,
which are like little hooks.
• Interlocking barbs keep contour feathers firm and
smooth.
EXTERNAL STRUCTURE
• Other types of feathers include down feathers,
which act as insulation, and filoplume feathers,
which have sensory functions.
EXTERNAL STRUCTURE
• Birds keep a clean plumage to rid the feathers and
skin of parasites.
• Preening, which is done by rubbing the bill over the
feathers, keeps the feathers smooth, clean, and in
place.
EXTERNAL STRUCTURE
• Secretions from an oil gland at the base of the tail
of many birds are spread over the feathers during
preening to keep the plumage water repellant.
• Secretions also lubricate the bill and legs to
prevent chafing.
• Anting is a behavior common to many songbirds and
involves picking up ants in the bill and rubbing them
over the feathers.
• The formic acid that ants secrete is toxic to
feather mites.
EXTERNAL STRUCTURE
• Feather pigments deposited during feather
formation produce most colors in a bird’s plumage.
• Color patterns are involved in cryptic coloration,
species and sex recognition, and sexual attraction.
EXTERNAL STRUCTURE
• All birds periodically shed and replace their feathers in a
process called molting.
• A typical molting pattern for songbirds begins after hatching
when the chick is covered with down.
• Juvenile feathers replace the down at the juvenile molt.
• A postjuvenile molt in the fall result in plumage similar to that
of an adult.
• Once sexual maturity is reached, a prenuptial molt occurs
late in winter or early spring, prior to the mating season.
• A postnuptial molt usually occurs between July and October.
EXTERNAL STRUCTURE
• Flight feathers are often lost in a certain order so
that birds are not completely deprived of flight
during molt periods.
• Many birds, however, such as ducks, coots, and
rails cannot fly during molt periods and will hide in
thick marsh grasses.
The Skeleton
• The bones of most birds are lightweight but very
strong.
• Some bones, like the humerus (forearm), have large
air spaces and internal strutting (reinforcing bony
bars), which helps increase strength.
• Birds also have a reduced number of skull bones,
and a lighter structure, the bill, which replaces the
teeth.
• Some aquatic birds, like the loon, have dense
bones, which helps reduce buoyancy during diving.
The Skeleton
• The appendages involved in flight cannot
manipulate nesting materials or feed young.
• The bill and very flexible neck and feet make these
activities possible.
• The cervical vertebrae have a saddle-shaped
surface that allows great freedom of movement.
• This flexibility allows the bill and neck to function
as a 5th appendage.
The Skeleton
• The pelvic girdle, vertebral column, and ribs are
strengthened for flight.
• Most ribs overlap the next rib to help strengthen
the rib cage.
• Fusion of the thoracic, lumbar, and sacral
vertebrae helps maintain the proper flight posture,
and supports the hind appendages during landing,
hopping, and walking.
The Skeleton
• The posterior caudal vertebrae are fused into a
pygostyle, which helps support the tail feathers
that are important in steering.
The Skeleton
• The sternum of most birds is very large for the
attachment of flight muscles.
The Skeleton
• The appendages of most birds have also been
modified.
• Some bones of the front appendages have been lost
or fused, and are points of attachment for flight
feathers.
• The rear appendages are used for hopping, walking,
running, and perching.
The Skeleton
• Perching tendons run from the toes across the
back of the ankle joint to muscles of the lower leg.
• When the ankle joint is flexed, as in landing on a
perch, these tendons contract and the foot grips
the perch.
• This automatic grasp helps a bird perch even while
sleeping.
Muscles
• The largest, strongest muscles of most birds are
the flight muscles.
• Muscles of most birds are adapted physiologically
for flight.
• These muscles must be able to contract quickly
and fatigue slowly.
• They also have many mitochondria and produce
large amounts of ATP to provide energy needed
for flight, especially long-distance migrations.
Muscles
• Domestic fowl have been selectively bred for
massive amounts of muscle (white meat).
• This is good for food, but poorly adapted for flight
because it doesn’t have enough mitochondria for
energy.
Flight
• The wings of birds are adapted for different kinds
of flight.
• Bird wings form an airfoil, which is a surface that
provides lift.
Flight
• Air passing over the wing travels farther and faster
than air passing under the wing, decreasing air
pressure on the upper surface of the wing and
creating lift.
Flight
• The lift must overcome the bird’s weight, and the forces that
propel the bird forward must overcome the drag that the
bird moving through the air creates.
• Increasing the angle that the leading edge of the wing makes
with the oncoming air (angle of attack) increases lift.
• As the angle of attack increases, the flow of air over the
upper surface becomes turbulent, reducing lift.
• Turbulence is reduced if air can flow rapidly through slots at
the leading edge of the wing.
• Slotting the feathers at the wing tips and the presence of an
alula (groups of small feathers that bones of the wing
support) help reduce turbulence.
Flight
• The tail of a bird helps with many things such as
steering and braking during flight.
• During horizontal flight, spreading the tail feathers
increase lift at the rear of the bird and causes the
head to dip for descent.
• Tilting the tail sideways turns the bird.
Flight
• When a bird lands, its tail deflects downward,
serving as an air brake.
• In the males of some species, like sunbirds and
widow birds, tails have dramatic ornamentation
that attracts females and improves reproductive
success.
Flight
• Different birds have different kinds of flight.
• During gliding flight, the wing is stationary, and a
bird loses altitude.
• Waterfowl come in for a landing using gliding flight.
Flight
• Flapping flight generates the power for flight and is
the most common type of flying.
• Soaring flight allows some birds to remain airborne
without using too much energy.
• Ocean soarers, such as albatrosses and frigate
birds, have long, narrow wings that provide
maximum lift at high speeds.
Flight
• Hummingbirds perform hovering flight.
• They hover in air by fanning their wings back and
forth 50-80 beats per second.
• The wings move in a figure 8 pattern.
NUTRITION AND DIGESTIVE
SYSTEM
• Most birds have huge appetites!!
• This appetite supports a high metabolism that
makes endothermy and flight possible.
• Bird bills and tongues are modified for many
different feeding habits and food sources.
• For example, a woodpecker tongue is barbed for
getting grubs from tree bark.
• Sapsuckers make holes in trees and use a brushlike
tongue for licking the sap that builds up in these
holes.
NUTRITION AND DIGESTIVE
SYSTEM
• The tongues of hummingbirds and other nectar
feeders roll into a tube for getting nectar from
flowers.
NUTRITION AND DIGESTIVE
SYSTEM
• Birds’ bills are used for feeding, preening, nest
building, courtship, and defense.
• Modifications of the bill reflect specific functions.
• The bill of an eagle is modified for tearing prey, the
bill of a cardinal is specialized for cracking seeds,
and the bill of a flamingo is used to strain food
from the water.
NUTRITION AND DIGESTIVE
SYSTEM
• In many birds, the crop is a storage structure that
allows birds to quickly ingest large quantities of
locally abundant food.
• They can then seek safety while digesting their
food.
NUTRTION AND DIGESTIVE
SYSTEM
• The crop of pigeons produces “pigeon’s milk”, a
cheesy secretion that young pigeons (squabs) feed
on until they can eat grain.
• Crops are less developed in insect eating birds
because they typically eat all day long.
NUTRITION AND DIGESTIVE
SYSTEM
• The stomach of birds is modified into 2 regions.
• The proventriculus secretes gastric juices that
start digestion.
• The ventriculus (or gizzard) has muscular walls to
help crush seeds and other hard materials.
• Birds may swallow sand and other hard objects to
help digestion.
• Most digestion occurs in the small intestine.
NUTRITION AND DIGESTIVE
SYSTEM
• Birds usually eliminate undigested food through
the cloaca.
• Owls, however, form pellets of fur, bone, and
feathers that are ejected from the gizzard through
the mouth.
NUTRITION AND DIGESTIVE
SYSTEM
• Birds are often grouped by feeding habits.
• These groupings aren’t always true because birds
may eat different kinds of food at different stages
of their lives.
• Robins mostly feed on worms when available.
• But in winter, they may feed on berries.
NUTRITION AND DIGESTIVE
SYSTEM
• Birds may directly conflict with human interests.
• Bird damage to orchard and grain crops costs
millions of dollars each year.
• Flocking and roosting habits of some birds, like the
European starlings and redwing blackbirds, put
millions of birds in one location, where they will
devastate fields of grain.
CIRCULATION, GAS
EXCHANGE, TEMPERATURE
• The circulatory system of birds is similar to reptiles,
except that the heart has completely separated
atria and ventricles.
• This separation prevents any mixing of highly
oxygenated blood with less oxygenated blood.
CIRCULATION, GAS
EXCHANGE, TEMPERATURE
• The bird heart is relatively large (about 2.4% of
body weight), and beats rapidly.
• Rates over 1000 beats per minute have been
observed in hummingbirds under stress.
• Larger birds have smaller hearts and slower heart
rates.
• An ostrich heart beats between 38-176 beats per
minute.
Gas Exchange
• The respiratory system of birds is very complex and
efficient.
• It consists of external nares which lead to nasal
passageways and the pharynx.
• Bone and cartilage support the trachea.
• A special voice box, the syrinx, produces bird
vocalizations.
• The lungs of birds are made of small air tubes
called parabronchi.
Gas Exchange
• It takes 2 breathing cycles to move air through the
respiratory system.
• During the first breath taken in, air moves into the
abdominal sacs.
• At the same time, air already in the lungs moves
through parabronchi into thoracic air sacs.
• When breathing out, air in the thoracic sacs move
out of the respiratory system and the air in the
abdominal sacs moves into the parabronchi.
• For the 2nd breath, air moves into the thoracic air
sacs, and is expelled during the next breath out.
Gas Exchange
• Because of high metabolism associated with flight,
birds consume more oxygen than any other
vertebrate.
• Bird lungs have almost a continual movement of
oxygen-rich air over their respiratory surfaces
during inhaling and exhaling.
Thermoregulation
• Birds maintain body temperatures between 100.4113 degrees.
• Lethal extremes are lower than 89.6 and higher
than 116.6.
• On a cold day, a resting bird will fluff its feathers
to increase insulation.
• It may also tuck its bill into the feathers to reduce
heat loss from respiratory structures.
Thermoregulation
• The most exposed parts of a bird are the feet and
tarsi, which have neither fleshy muscles or a rich
blood supply.
• Temperatures in these extremities are allowed to
drop to near freezing to prevent heat loss.
• Shivering also generates heat in extreme cold.
• An increase in metabolism during the winter
months requires extra food.
Thermoregulation
• Some birds will allow their body temperatures to
drop on cool nights.
• For example, whip-poor-wills allow their body
temperature to drop from about 104 down to 60.8
and respiration becomes very slow.
• Muscular activity during flight produces large
amounts of heat, which birds can get rid of by
panting.
NERVOUS AND SENSORY
SYSTEMS
• Birds have many sensory adaptations.
• The forebrain of birds is much larger than that of
reptiles.
• The cerebral hemispheres are larger, including a
region of gray matter, the corpus striatum.
• The corpus striatum helps in visual learning,
feeding, courtship, and nesting.
• The midbrain also receives sensory input from the
eyes.
• The hindbrain includes the cerebellum and the
medulla oblongata, which help motor activities and
regulate heart and respiratory rates.
NERVOUS AND SENSORY
SYSTEMS
• Vision is a very important sense for birds.
• The structures of bird eyes are similar to other
vertebrates, but bird eyes are much larger relative
to their body size.
• The eyes are usually flattened in the back, but
birds of prey have eyes that protrude in the front.
NERVOUS AND SENSORY
SYSTEMS
• Birds have a unique double focus mechanism.
• This allows an osprey or other bird of prey to
remain focused on a fish while rapidly descending
from the air.
NERVOUS AND SENSORY
SYSTEMS
• The retina of a bird’s eye is thick and contains both
rods and cones.
• Rods help in low light intensity and cones are active
under high light intensity.
• Cones are especially thick in an area called the
fovea.
• Some birds have 2 fovea per eye.
• One is the “search” fovea because it gives them a
wide angle of vision.
• The other is the “pursuit” fovea and allows for
depth perception.
NERVOUS AND SENSORY
SYSTEMS
• The position of the eyes on the head also affects
their vision.
• Pigeons have eyes located on the sides of the head,
giving them almost 360 degree wide view, but
narrow depth perception.
• They don’t have to pursue their food (grain) but
can stay alert for predators while on the ground.
• Hawks and owls have eyes more forward on the
head.
• This helps their depth perception.
NERVOUS AND SENSORY
SYSTEMS
• Birds also have a nictitating membrane that helps
to cleanse and protect the eye.
• Smell is not very important to most birds.
• Exceptions are turkey vultures who use their sense
of smell to locate dead prey.
• Most birds have well-developed hearing.
• Loose, delicate feathers called auriculars cover
the external ear opening.
• Middle and inner ear structures are similar to
reptiles.
• Birds hear about the same as humans.
EXCRETION AND WATER
REGULATION
• Birds excrete uric acid, which is temporarily stored
in the cloaca.
• Water is also reabsorbed in the cloaca.
• Some birds have salt glands that drain excess salt
through the nasal openings to outside the body.
• These are very important to marine birds that drink
saltwater and feed on invertebrates that have large
amounts of salt in their tissues.