02
Mar
10

Bird Navigation Ability Revealed?

Looks like we may finally understand how birds can make such amazing migrations and know exactly where to go despite the amazing lengths that some of them go to from year to year. Seems that there are iron particles in nerve endings in their beak.

Iron containing short nerve branches in the upper beak of birds may serve as a magnetometer to measure the vector of the Earth magnetic field (intensity and inclination) and not only as a magnetic compass, which shows the direction of the magnetic field lines.

“After we had shown the system of dendrites with distinct subcellular iron-containing compartments in homing pigeons, immediately the question was posed whether similar dendritic systems may be found in other bird species, too,” as Gerta Fleissner, the principal investigator, comments. Meanwhile they could describe similar candidate structures in the beaks of various avian species. X-Ray-fluorescence measurements at DESY demonstrated that the iron oxides within these nervous dendrites are identical. These findings were published few days ago in the high-ranking interdisciplinary online journal Plos One.

More than about 500 dendrites in the periphery encode the magnetic field information, which is composed in the central nervous system to a magnetic map. It obviously does not matter, whether birds use this magnetic map for their long distance orientation or do not — the equipment can be found in migratory birds, like robin and garden warbler, and well as in domestic chicken. “This finding is astonishing, as the birds studied have a different life styles and must fulfil diverse orientational tasks: Homing pigeons, trained to return from different release sites to their homeloft, short-distance migrants like robins, long-distance migratory birds like garden warblers and also extreme residents like domestic chicken,” explains Gerta Fleissner.

Specialized iron compounds in the dendrites locally amplify the Earth magnetic field and thus induce a primary receptor potential. Most probably each of these more than 500 dendrites encodes only one direction of the magnetic field. These manifold data are processed to the brain of the bird and here — recomposed — serve as a basis for a magnetic map, which facilitates the spatial orientation.

If you are not familiar with bird migration it is worth looking up. It will amaze you how these bird-brained featherweights can make a journey of hundreds or even thousands of miles and make the journey precisely every time. Some, like the tiny Plover migrate across open ocean to land in Hawaii every year, and they have no reserves left to find other land should they make a mistake. Some even travel up to 40,000 miles a year returning to breeding and feeding grounds time and again.

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