Birds

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Birds
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What is a bird?

• Birds inhabit a variety of environments around
  the world, including Antarctica, deserts, and
  tropical rain forests.
• Biologists sometimes refer to birds as feathered
  dinosaurs.
• Fossil evidence seems to indicate that birds have
  evolved from small, two-legged dinosaurs called
  theropods.

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• Like reptiles, birds have clawed toes and protein
  scales on their feet.
• Fertilization is internal and shelled amniotic
  eggs are produced.
• Some birds are flightless, all birds have
  feathers and wings.

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Feathers

• A feather is a lightweight, modified protein
  scale that provides insulation and enables
  flight.
• Preening running its bill through the feathers
  to keep them in good condition for flight. It
  also rubs oil from a gland near the tail into the
  feathers.
• Feathers are also good insulators because they
  reduce heat loss. They also help in waterproofing
  the bird.

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Feathers continued

• Molting shedding of old feathers and the growth
  of new feathers.
• Usually in late summer
• Dont lose all their feathers at one time and are
  able to fly while molting.
• Wing and tail feathers are usually lost in pairs
  so the bird can maintain a balance.

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Wings

• Powerful flight muscles are attached to a large
  breastbone called the sternum and to the to the
  upper bone of each wing.
• It supports enormous thrust and power produced by
  the muscles as they move to generate the lift
  needed for flight.

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Energy

• Flight requires high levels of energy.
• A birds four chambered, rapidly beating heart
  moves oxygenated blood quickly throughout the
  body. This circulation supplies cells with the
  oxygen needed to produce energy.
• Respiratory system supplies oxygenated air to the
  lungs when it inhales as well as when it exhales.

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Breathing Cycles

• 1. Inhalation oxygenated air passes through
  the trachea and into the lungs where gas exchange
  occurs. Most air passes directly into the
  posterior air sacs but some goes directly to the
  lungs.
• 2. Exhalation deoxygenated air is removed from
  the lungs, oxygenated air returns to the lungs
  from the posterior air sacs.
• 3. The next inhalation, deoxygenated air in the
  lungs passes into the anterior air sacs.
• 4. Finally, at the next exhalation, air passes
  from the anterior air sacs out of the trachea.

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Endotherms

• Birds are able to maintain the high energy levels
  needed for flight because they are endotherms.
• Endotherm is an animal that maintains a nearly
  constant body temperature that is not dependent
  on the environment.
• Feathers help with insulation. When in high
  temperatures, birds flatten their feathers and
  hold their wings away from their body. They also
  pant to increase respiratory heat loss.
• Allows bird to live in all environments.
• Endotherms must eat large amounts of foodto
  sustain high energy levels.

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Reproduction

• Bird have internal fertilization and lay amniotic
  eggs usually inside a nest.
• Eggs are encased in a hard shell, unlike the
  leathery shell of reptiles.
• Birds do not leave the eggs.
• Incubate or sit on their eggs to keep them warm.
  Also, turn eggs to help them develop properly.
• Some species the male and female sit on nest in
  others only one does.

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Hollow Bones
Wings
Beak
Air Sacs
Legs
Digestion
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• Wings Birds have a variety of wing shapes and
  sizes. Some birds have longer, narrower wings
  adapted for soaring on updrafts, whereas others
  have shorter, broader wings adapted for quick,
  shirt flights among the forest trees.
• Hollow Bones The hollow bones of birds are
  strengthened by bony crosspieces. The sternum is
  the large breastbone to which powerful flight
  muscles are attached.
• Beaks Birds have beaks, sometimes called bills,
  covered by a protein called keratin, but they do
  NOT have teeth.

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• Legs The legs of birds are made up of mostly
  skin, bone, and tendons. The feet are adapted to
  swimming, perching, walking, or catching prey.
• Digestion The digestive system of a bird is
  adapted for dealing with large quantities of food
  that must be eaten to maintain the level of
  energy necessary for flight. Because birds have
  no teeth, many swallow small stones that help to
  grind up food in the gizzard.
• Air Sacs About 75 of the air inhaled by a bird
  passes directly into the air sacs rather than
  into the lungs.

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Diversity of Birds

• Depends on the environment in which they live and
  the food they eat.
• Ptarmigans feathered legs and feet that serve
  as snowshoes in the winter, making it easier for
  the birds to walk in the snow.

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• Penguins are flightless birds with wings and
  feet modified for swimming and a body surrounded
  with a think layer of insulating fat.

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• Large eyes, an acute sense of hearing and sharp
  claws make owls well-adapted, nocturnal predators
  able to swoop with absolute precision onto their
  prey.

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Shape of Beaks

• Hummingbirds have long beaks that are used to
  obtain nectar from flowers.
• Hawks have curved beaks that are adapted for
  tearing apart their prey.
• Pelicans have huge bills with pouches that they
  use as nets for capturing fish.
• A cardinals stout beaks are for cracking seeds.

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Cardinal
Hawk
Hummingbird
Pelican
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Origins of Birds

• Scientists hypothesize that todays birds are
  derived from an evolutionary line of dinosaurs
  that did not become extinct. The earliest known
  bird in the fossil record is Archaeopteryx.