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How do Birds Find Their Way?

How do Birds Find Their Way?. What we learned in the last 20 years. Introduction. Given the power of flight, birds are highly mobile. Some species migrate and travel great distances. Arctic Tern - 12,000 mile journey. Manx Shearwater – Boston to Wales. Previous Studies.

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How do Birds Find Their Way?

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  1. How do Birds Find Their Way? What we learned in the last 20 years

  2. Introduction • Given the power of flight, birds are highly mobile. • Some species migrate and travel great distances. • Arctic Tern - 12,000 mile journey. • Manx Shearwater – Boston to Wales

  3. Previous Studies • Matthew’s Sun-Arc Theory • Birds look at the movement of the sun and compares angles and the noon azimuth to extrapolate latitude and longitude coordinates. • Kramer’s Map and Compass Hypothesis • Birds establish a “Map” (direction to the goal) with the help of an external reference, a compass.

  4. Current Studies • Landmarks • Stars • Ultraviolet Light • Infrasounds • Sun • Magnetic Fields • Olfaction

  5. Landmarks • Pigeons tested using frosted contact lenses. • There is some indication that birds use landmarks, at least sometimes. • Not effective at night.

  6. Stars • Many birds migrate at night. • “Cluster N” – Mouritsen et al. 2005 • Indigo Buntings seem to use the northern sky within about 35 degrees of the north star. • Problematic in cloudy conditions and in Southern hemisphere.

  7. Ultraviolet Light • Study by Parrish et al. demonstrated birds can detect ultraviolet light. • Effective even during cloudy days. • Not readily studied.

  8. Infrasounds • Low Frequency Sounds (<10 Hz) • Generated by wind, ocean waves, storms, mechanical devices, etc. • Conditioned Cardiac Response • Pigeons hear less than 2 Hz. • Not readily studied

  9. Sun • Sun acts as a compass (angles of light/shadow) • Birds possess internal circadian clock. • On cloudy days, Blue-winged Teal would circle until they got above the clouds at which time they started to move in the appropriate direction.

  10. Magnetic Field • Birds have magnetodetection senses (Mouritsen and Ritz 2005). • Birds have magnetite near the beak. • Cryptochromes in the eyes. • Exact mechanism still unclear. • Possible problems

  11. Smells • Intact sense of smell is necessary for goal-oriented homing of pigeons. • Olfactory-based mechanism linked to piriform cortex. • Trace gases/ratio of hydrocarbons at the home site distributed via winds may serve as a navigational cue (Wallraff 2005)

  12. Which one(s) do they actually use? •   Most early studies on navigation tried to explain it by one mechanism. • Orientation and navigation may be due to a variety of cues • Path determined primarily by the sun. The magnetic field assists as a guide (Wikelski et al. 2004)

  13. Does this apply to all birds? • Wikelski seems to think so. • “It's such a simple and elegant mechanism that I would say it is widespread.” • Species vary in their navigational ability. • i.e. Pigeons. • Studies largely consist of a few species and are lab oriented.

  14. Conclusion • Despite all the theories and experiments dealing with navigation, there is much that is still not understood about how birds determine their position in relation to a fixed goal.

  15. Future Research • Is the sun used to calibrate the magnetic compass? – Cochran et al. 2004 • Extend analyses beyond homing pigeons and laboratory analyses. • See how findings compare with other species (Salmon, Turtles, Sharks, etc).

  16. Questions?

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