Bird%20Navigation

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Bird Navigation

• Tony Ludlow
• tony.ludlow_at_modelresearch.com
• www.modelresearch.com
• 12th Jan 2006

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Aims of lecture

• Show what birds achieve
• Discuss views about how they do it
• Illustrate the way various systems interact and
  how birds calibrate one system from another
• Review mistakes in the progress of research

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Types of navigation

• Piloting
• Compass sense
• True navigation

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Piloting

• Difficult to rule out, given height at which
  birds fly
• Not possible for Bronze-winged cuckoos
• Other methods can be demonstrated

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Compass v true navigation

• Perdecks experiments
• Tracking birds

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Perdeck (1958)
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Michener and Wallcott's pigeon harness
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Combination of methods

• Michener and Wallcott (1967) tracked single
  pigeons and found
• A phase of straight flight, not usually towards
  home compass sense
• Flight heading accurately towards home true
  navigation
• Use of landmarks within 10 miles of loft.

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Michener and Wallcott (1967) tracks
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Sensory cues problems in research

• Circular statistics
• Redundancy not understood (Pennycuick, Matthews)
• Vanishing direction
• Piloting cues not eliminated

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Kramer (1957)

• Starlings --- day migrants
• Circular cage recorded from each perch
• Birds showed migratory direction
• Confused by overcast
• Adjusted for sun movement (90 degrees in 6 hr)

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Sun compass Kramer (1957)
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Kramer (1957)

1. Compensated for normal sun movement
2. Followed sun when it was shifted by mirrors (so
   not magnetism, etc.)
3. 6hr clock shift caused 90 deg shift
4. Sun kept stationary birds changed their angle
   to it.

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Stellar compass

• Sauer and Sauer (1955) showed blackcaps chose
  correct autumn directions under a planetarium and
  reversed direction in spring
• Emlen (1970) showed that indigo buntings respond
  to celestial rotation they were taught to use
  other constellations as north star
• Bellrose (1967) used radar to show that migrants
  were well oriented at night, even in overcast
• May be they see glimpses and keep straight using
  the direction of wind gusts (Nisbett, 1955)

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Magnetic compass

• Rejected in 1960s
• Evidence in bees (eg. Lindauer and Martin, 1972)
• Keeton (1971) showed magnets confused pigeons
  under overcast (could act on compass or true
  navigation)
• Wiltschko and Wiltshcko (1972) showed that robins
  responded to the angle of dip if strength of
  field similar to earth's
• Wallcott and Green used electric coils on
  pigeons. NUP disoriented, SUP did not.

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Polarised light

• Brines (1980) demonstrated that rotation of
  polarised light was used during day
• Seems to be this rather than the sun which is
  used
• Birds use rotation of stars to find north
• Using rotation, they dont need a clock

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True navigation

• Perdeck's adult starlings showed true navigation
• So did Michener and Wallcott's tracks
• The vanishing direction is easy to measure but
  very often wrong.

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Theories of true navigation

• Every twist and turn is integrated (spider,
  millipedes, Walraff (2000))
• Celestial cues could be used to find home
  direction (Board of longitude prize)
• Magnetic variation across earth's surface
• Odours

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Celestial navigation?

• Requires astonishing accuracy of time sense
• Requires astonishing accuracy of visual
  discrimination (frosted glass contact lenses)
• Keeton showed that pigeons home when they cannot
  see the sun
• After a time shift, pigeons show compass errors
  not errors in home direction.

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A magnetic map?

• Pattern of magnetism over earth's surface could
  be used in principle
• Wiltschko and Wiltschko (1996) showed this would
  require minute discrimination 0.03. Daily
  variations are of same order.
• It is not clear how the map would work Angle of
  dip Boles Lohmann (2003) lobsters

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Home direction from odours

• Wallraff (1967) reared pigeons in screened lofts
• Those which could see the sun but not feel the
  wind got lost
• Those which felt the wind but never saw the sun
  were fine
• Odour hypothesis
• From 1972 Papi and colleagues did many
  experiments on anosmic pigeons
• There is a debate in the Navigation symposium.
  See Wallraff (1996) Wiltschko (1996) and Able
  (1996)
• Odetti et al (2003) effects of flight experience
  on orientation performance

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Calibrating the systems

• Birds are not born with a star map
• Magnetic compass (angle of dip) reverses at the
  equator, so needs to be recalibrated
• Savannah sparrows are born with a response to
  magnetic field
• Helbig (1996) Genetics of response
• Migratory song birds also respond to celestial
  rotation
• Celestial compass updates the magnetic one during
  migration
• But Sandberg et al (2000), 4 species calibrate
  star map with magnetic cues.

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Redundancy and balance between systems

• Keeton sun or magnets
• Multiple systems
• How much weight does a bird put on each
• Learning two cues could mean less weight to each
• Individuals may differ, based on their
  experience. That would make experiments hard to
  interpret