The secrets of homing pigeons are set to be revealed after the creation of an ultra-lightweight flight recorder that uses satellite tracking to plot each bird's exact course.
The matchbox-sized Global Positioning System tracker developed by Karen von Huenerbein, a biologist at the University of Frankfurt, Germany, is strapped to the back of each bird with teflon ribbons.
Just how homing pigeons are able to navigate home from locations they have never visited is still a mystery, though birds have been tracked by sight, heavy radio packs and even from aircraft.
Avian flight recorders have been developed for long-range migrations or short journeys, but until now there have been no cheap, reliable systems that can be used for birds flying the mid-range distances of homing pigeons.
Von Huenerbein's flight recorder consists of a hybrid GPS board, a tiny antenna, a 3V lithium battery, and a microprocessor. It weighs 33g -the bird typically weighs between 300 and 500g -and has a battery lifetime of three hours.
When the pack is recovered, the scientists can download its data and track the pigeon's route to a resolution of 30m, with a position recorded every second.
Specially trained pigeons have now made 120 test flights over a 30km course. During the trials, von Huenerbein has watched pigeons begin their flights by tracing extensive loops around their starting points, select a variety of routes to avoid hills, take rests of between a minute and several hours and make sudden detours that suggest encounters with other pigeons or even predators.