Consistent effect of an attached magnet on the initial orientation of homing pigeons, Columba livia

► Homing pigeons were released carrying small rare-earth magnets or brass weights (control) on their ceres. ► Vanishing direction of magnet-carrying pigeons was consistently shifted clockwise. ► North-up orientation of the magnet had a stronger effect than South-up orientation. ► Results were consistent for releases at various distances and directions from the birds' home loft. ► Our findings suggest that magnets may affect homing pigeons' magnetic map, magnetic compass or circadian clock.