World Magnetic Model – Why in News at Today?

CONTEXT:

  1.  Every year, billions of songbirds migrate thousands of miles between Europe and Africa — and then repeat that same journey again, year after year, to nest in exactly the same place that they chose on their first great journey.
  2. The remarkable navigational precision displayed by these tiny birds — as they travel alone over stormy seas, across vast deserts, and through extremes in weather and temperature — has been one of the enduring mysteries of behavioural biology.
  3. Birds buffeted by winds so much that they’re significantly displaced from their migratory route are able to realign their course if they’ve already performed one migration.
  4. This has suggested that birds’ navigational abilities, some of which is built around a sense of compass direction, includes a mechanism for finding their way back home from parts of the world they’ve never before visited.
  5. New study of Eurasian reed warblers has found that this remarkable ability involves a “magnetic map” that works like our human system of coordinates.
  6. Surprisingly, the study found that these birds understand the magnetic field of places thousands of miles into territory they’ve never before visited — suggesting some birds could possess a “global GPS system” that can tell them how to get home from anywhere on Earth.

MIND MAPS:

  1. It’s long been known that adult birds develop some sort of navigational map to help them migrate.
  2. How they do this has remained controversial. Several cues have been proposed as guides for migratory birds — including odours, infra-sound, and even variations in gravity.
  3. However, a gathering body of evidence has indicated that the Earth’s magnetic field is one of the likeliest solutions to this mystery.
  4. It has been suggested that different parameters of the Earth’s magnetic field could form a grid, which birds follow, of north-south and east-west lines.
  5. That’s because magnetic intensity (the strength of the magnetic field) and magnetic inclination (the angle formed between the magnetic field lines and the surface of the Earth, also called the “dip” angle) both run approximately north to south.
  6. Magnetic declination – the difference between the direction to the magnetic north pole and the geographical north pole — provides the east-west axis.
  7. Despite largely agreeing that certain birds navigate via the Earth’s magnetic field, scientists haven’t worked out precisely what sensory apparatus they use to detect it – or whether multiple systems are used to detect different parameters of the field.
  8. Other animals, like turtles, can also sense the magnetic field, but the same uncertainties apply.
  9. Regardless, if birds have learned that magnetic intensity increases as they go north, they should be able to detect their position on the north-south axis wherever they happen to be.
  10. Similarly, if they experience a declination value that is greater than anything they’ve previously experienced, they should know they’re further east.
  11. On this basis, the theory is that they can calculate their position on the grid and correct their orientation.
  12. This would mean that birds essentially navigate using a system similar to our Cartesian coordinates – the basis of modern GPS navigation.
  13. If this coordinates theory is accurate, it would mean that birds should be able to use their knowledge of magnetic field parameters to estimate their location anywhere on Earth – through the extrapolation or extension of their navigational rules.
  14. To date, there has been no clear evidence that birds can use the magnetic field in this way.