Homing pigeons are well known for their extraordinary sense of direction, which is thought to result from a specialised sense that allows them to navigate using the Earth's magnetic field.
New research, published today in Nature has revealed that cells previously thought to be the centre of the magnetic sense in birds are instead non-magnetoreceptive macrophage (white blood) cells.
This important finding has reset current thinking in avian magnetic navigation and places the field back on course for the search for the true location of the magnetic sense in birds.
Dr Jeremy Shaw and Professor Martin Saunders of The University of Western Australia's Centre for Microscopy, Characterisation and Analysis assisted with the characterisation of these macrophage cells as part of an international study of homing pigeons.
Scientists are also investigating if similar navigational tools are used by other animal species such as bees, rainbow trout and sea turtles.
Dr Shaw worked on this project with Dr David Keays, an Australian who now works at the Institute of Molecular Pathology in Vienna, Austria.
"It took a team of Australians and Austrians to show that the established dogma in the field was completely wrong. The mystery of how animals detect magnetic fields has just got more mysterious," Dr Keays said.
Dr Shaw and his team at UWA used transmission electron microscopy (TEM) analysis - a beam of high-energy electrons passing through thin samples of pigeon tissue - to characterise the distribution and type of iron minerals present.
"Our contribution confirmed that the iron in the macrophage cells in the pigeon beak were normal iron deposits composed primarily of protein bound iron in the form of ferrihydrite, similar to that found in many other animals. Magnetite is thought to be the likely candidate magnetic material," Dr Shaw said.
Macrophages are found in the spleen, skin and lungs of many animals and have a vital role in defending against infection and in the re-cycling of iron from red blood cells.
In addition to the beak, similar iron-rich cells were also found in the pigeons' feather follicle and skin cells, showing that they are widely distributed through the body.
Scientists are now working to establish the exact mechanism by which migratory birds respond to magnetic fields and are hoping to link their findings to other species.