Seabirds Smell Their Way Home
There has always been a keen debate about whether birds find their way home using the earth’s magnetic field or alternatively, their senses of sight and smell. There is almost certainly no simple answer to the riddle. However, researchers from Oxford University, together with scientists from the Universities of Barcelona and Pisa, have recently demonstrated that smell is a factor in the navigation of seabirds.
The Shearwaters of Menorca
An experiment was conducted recently by researchers off the coast of the Spanish Island of Menorca. Miniature GPS loggers were attached to shearwaters which were nesting in crevices and caves on the island. The birds when were then tracked as they foraged at sea. Their flights involved travelling over many miles of featureless water and so they would be unable to navigate by sight alone.
Isolating the Sense of Smell
The birds were split into three groups. One group had its sense of smell removed temporarily, another carried small magnets and a control group was left alone. All of the birds were able to forage for food, gain weight and incubate their eggs but the birds with a restricted sense of smell had more difficulty navigating their way home when they flew out of sight of the land.
The birds which struggled showed signs of improvement when they reached the coast and could navigate by sight using familiar features of the landscape. The researchers were able to conclude that the seabirds made use of an olfactory map when out at sea. The birds use in-built maps of odours which enable them to navigate over thousands of miles of featureless Ocean.
Senior author of the ensuing report, Tim Guilford, Professor of Animal Behaviour and leader of the Oxford Navigation Group in Oxford's Department of Zoology, said: 'To the best of our knowledge, this is the first study that follows free-ranging foraging trips in sensorily manipulated birds.'
He further explained that navigating across the ocean is a serious challenge for the birds because of the sheer size of the area that the birds must cover and the lack of identifiable landmarks.
Previous studies exploring seabird navigation have utilised displaced birds and it was felt that this method was influencing the outcome of the experiments. The new study looked at native birds in their existing environment. It is now hard to argue that birds don’t use their sense of smell in order to navigate the oceans.