Iron-containing cells in the beaks of pigeons were thought to be the magnetic field receptors responsible for the pigeon's famous navigational abilities. However, research published in Nature shows that this is not the case and the search for the elusive magnetoreceptors must go on.
The international team showed that the cells are macrophages (an immune cell) and not the nerve cells that magnetoreceptors are likely to be. By using sophisticated microanalysis in the Australian Microscopy & Microanalysis Research Facility at the University of Western Australia authors Dr Jeremy Shaw and Prof. Martin Saunders showed that the iron inside the cells was not in the mineral form that might be expected for a magnetoreceptor. Macrophages all over the body contain iron from the breakdown of old red blood cells. The macrophage cells in the beak are no different.
Dr Shaw worked on this project with Dr David Keays, an Australian who now works at the Institute of Molecular Pathology in Vienna.
“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,” said Dr Keays.
“Our contribution confirmed that the iron in the pigeon beak macrophage cells was a normal iron deposit, 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.
The search for the actual mechanism that allows migratory birds, and many other animals, to respond to the Earth's magnetic field and navigate around their environment therefore remains an intriguing puzzle to be solved.