Knowledge is the antidote to fear.

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Knowledge is the antidote to fear. - Ralph
Waldo Emerson
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Chapter 21 BirdsMs.Cox
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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.

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Introduction

• Birds however have some things that are unique to
  them
• Feathers, wings, endothermy, modified vertebral
  column, light bones, horny bill without teeth.

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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.

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Ancient Birds
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Fossil Remains
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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

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Characteristics

• Feathers- also called plumage
• Function to allow flight, help species recognize
  one 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.

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Contour Feathers

• Structure of Contour Feathers
• 1. Consist of a vane with its inner and outer
  webs, 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.

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Hamuli- Hook
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Parts of the Feather
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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.
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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.
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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.
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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.
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Diversity of Feathers
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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.

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An Egret Preening
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Color of Feathers

• Feather pigments are deposited during feather
  formation most colors in a birds 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.

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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.
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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.

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Duck Molting- this takes a couple of weeks
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Other birds molting
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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.

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Elephant Bird Skeleton
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Skeleton Drawing
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Key to worksheet

• 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 

• 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)

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The bonesWhile 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.

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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.

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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.

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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.

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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.

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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.

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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.

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Foot Types
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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.
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WOODPECKERS have two toes pointing forwards and
two backwards for climbing up, down, and
sideways on tree trunks.
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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.
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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).
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RAPTORS such as hawks, eagles, and owls use large
claws (called talons) to capture, kill, and carry
prey with their feet.
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Pheasants and chickens use their strong feet to
scratch the dirt and leaf litter to uncover seeds
and insects.
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Strong-legged flightless birds, like the
Cassowary, protect themselves by kicking with
their powerful feet and sharp claws.
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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.

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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.

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Types of Nests

• 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.

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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 "hide-out" during inclement weather.
  Cavity-nesting 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.

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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. 

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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.

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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  

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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.

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• 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.

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Digestion

• 3. 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.

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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.

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• 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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• 6. 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. 

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• 7. 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.

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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.

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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.

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Beaks

• Hummingbirds have long, tubular bills that
  resemble straws, which they use to sip nectar
  from flowers

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Mergansers, specialized for eating fish, have
sharp tooth-like structures on the edge of the
bill to hold fish tightly.
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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.
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The edges of a Mallard's bill are fringed to
strain plants, seeds, and small animals from mud
and water.
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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.
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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.

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• 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"
  ?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. 

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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

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• 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.

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Respiration
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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! 

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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 Neo-tropical
  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. 

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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.

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Bird on a Mission
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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
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Migration
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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.

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• 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.

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Brood Parasitism
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Brood Parasitism
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Brood Parasitism