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MIGRATION AND NAVIGATION

VIEWS: 3 PAGES: 11

  • pg 1
									MIGRATION AND
 NAVIGATION
                Migration
• Not all birds migrate
• Greatest adventure and greatest risk for
  those that do
           Migration routes
• Routes are usually south in winter and north
  in summer
• Usually breed in the north
• Some routes are short, some take 50-60
  days
       Stimulus for migration
• Lengthening of days stimulates gonad
  development and fat accumulation
    Direction finding in migration
• Visual mostly  use landmarks, etc.
• Innate sense of time and direction
• Can detect and navigate magnetic field
• Maintain compass direction using the sun
  and stars
• Only best navigators survive
        Reproductive system
• Males have 2 testes, sperm travels through
  vas deferens into cloaca
• Female has one left ovary that passes eggs
  down oviduct
• Cloacas press together and sperm is passed
  into female
• As eggs pass down the oviduct, albumin
  (egg white) is added and shell is secreted
            Mating systems
• Most practice monogamy
  – Swans and geese keep same partners for life
  – Seasonal monogamy is most common
             Mating systems
• Polygyny: male mates with more than one
  female
  – Grouse: male chosen for genetic quality
  – Territoriality and courtship is varied by brightly
    colored feathers, song, flight, etc.
     Nesting and care of young
• Some make nest and some do not
• Try to avoid predation and use grass, twigs,
  mud, etc.
• 2 types of newly hatched bird:
  – Precocial: covered with down when hatched
    and can run and swim as their plumage drives
  – Altricial: naked and helpless
     • Both require care from parents and eat more than
       their weight everyday
    Precocial vs altricial
•              •

								
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