Movements and Migration

Chapter 5--Ridley

Modified: 2007-11-19

---

Migration

• Questions
  • Why?
    • Change in environments (a given, btw)
    • Track beneficial changes in environment
  • How?
    • Planned migration
      • Animals track local conditions and respond
      • Wildebeest track rain using visual and auditory cues
    • Seasonal migration
      • Animals anticipate regular environmental changes
      • Regular environmental changes include: seasons, daylight length, and biologically correlated changes (leaves falling, vegetation loss)
      • Requirements
        • Accurate environmental cue
        • Compass sense
      • Examples

        • Monarch Butterflies
        • Shortening daylight is likely cue
        • Need to avoid cold is another factor

      • Lemmings
        • Overcrowding is cue
        • Picture
      • Passenger Pigeon
        • Extinct species that once migrated seasonaly in large numbers in North America
        • Picture
      • American Bison (buffalo)
        • Nearly driven to extinction
        • Migration was seasonal in North American midcontinent
        • Picture
      • Arctic Tern
        • Migrates seasonally from Arctic to Antarctic
        • Artic Tern
        • Blackpoll Warbler Migration Route
      • Gray Whale
      • Migrates from Bering Sea to Baja California seasonally
        • Picture

Homing

• Three Possibilities
  • Memorize local landmarks
    • Digger Wasps
    • Tinbergen's research
    • Picture and Animation, Another picture
  • Home site is recognizable at a distance
    • Salmon migration
    • Picture
  • Internal map sense
    • Pigeon navigation
      • True navigation
        • Time corrected solar compass
          • Used when sun is out
        • Magnetic sense
          • Used when overcast
          • Brass, Magnets, and Helmholtz Coils
        • Olfaction
          • Used when overcast
      • Use landmarks
        • SAU Water Tower
        • Roads
      • Learning
        • Young pigeons are less able to navigate
        • Clockshifting experiments
    • Picture Magnetic Effects  

URLS

Animal Migration Basics

Sooty Shearwater Migration

NY Times: Migration in Sudan