Pigeon riddle flies in the face of science

Scientists have sent robot scouts into deep space and unravelled the genome, yet they have been forced to admit they were still baffled by how homing pigeons navigate. Experts at Vienna's Institute of Molecular Pathology said they had overturned claims that the birds' feat is due to iron-rich nerve cells in the beak that are sensitive to Earth's magnetic field. "It was really disappointing," molecular biologist David Keays told AFP after years of endeavour. "The mystery of how animals detect magnetic fields has just got more mysterious." Keays' team used 3-D scanners to search for the cells and sliced pigeon beaks into 250,000 wafer-thin slivers for analysis. They found that the particles credited with the pigeon's homing skills were actually macrophages, a type of white blood cell which protects the birds from infection and had no connection to the brain. "They are not excitable cells and cannot produce electric signals which could be registered by neurons (brain cells) and therefore influence the pigeon's behaviour," the researchers said. Nor are these cells exclusive to the beak. Keays described the process as "extremely frustrating" but insisted the findings should...