Seabirds use sense of smell to map routes

SEABIRDS find their way thousands of miles across featureless oceans – thanks to a keen sense of smell, according to new research.

An analysis of flight patterns found the expert navigators use an “odour map” – a mental patchwork picture of local fragrances – to guide them.

And scientists now believe the phenomenon may be common in the animal kingdom, having a role in movements such as mass migrations and finding food.

Seabirds fly for many days and nights across water to their preferred feeding locations and then return to their nests without getting lost.

How they do this has been debated for years but a study of three species of shearwaters, known for their long-distance migrations, may finally have solved the mystery.

Dr Andrew Reynolds and colleagues tagged 210 individuals with GPS monitors and found seven in ten used olfactory cues to navigate, and almost all of them did it on long journeys.

They relied on an established mathematical theory that accounts for how odours disperse in the atmosphere and how birds can use them.

Dr Reynolds, of Rothamsted Research in Hertfordshire, explained: “When the odours are continually present above the threshold of detection, then the ‘odour map’ is present and the birds will maintain nearly unidirectional flight.

“But when the odour concentration falls below this level, the birds are without their map and so effectively lost. They may change course either because they become disoriented or because they are attempting to reestablish contact with the odour map.”

A previous study had shown shearwaters deprived of their sense of smell showed dramtically impaired homing ability, but this is the first time it has been proved in the wild without interfering with their sensory powers.

It backs earlier evidence that albatrosses, petrels and other “tube-nosed” seabirds fly thousands of miles over open ocean and navigate back to their nests on tiny, remote islands thanks to a refined sense of smell.