Aug. 14, 2006 — Italian researchers may have solved the puzzle of what makes homing pigeons such legendary navigators — they simply follow their noses.
In a real life homing experiment, Anna Gagliardo of the University of Pisa and colleagues tested the birds’ magnetic sensing and olfactory systems in order to establish how they make their extraordinary navigations across hundreds of miles.
The research, published in the current issue of the Journal of Experimental Biology, followed a 2004 laboratory study by Cordula Mora and colleagues from the University of Auckland, New Zealand.
In this research, Mora conditioned pigeons to detect an anomaly in a magnetic field. Mora showed that pigeons detected a magnetic stimulus in their upper beaks by using the ophthalmic branch of the trigeminal nerve (the largest cranial nerve).
The 2004 study reinforced the theory that homing pigeons navigate by using tiny magnetic particles in their beaks to map changes in the Earth’s magnetic fields.
But Gagliardo argues just because the pigeons have the ability, doesn't mean they always use it.
"They do have the ability to detect magnetic fields, but this doesn’t mean they use it to navigate," Gagliardo told Discovery News.
To test how much the birds use this sense, Gagliardo cut a section of the olfactory nerve in 24 homing pigeons and a section of the ophthalmic branch of the trigeminal nerve in another 24. A third group of 24 birds underwent sham operations and served as a control group.
Gagliardo then released the three different groups of inexperienced homing pigeons 30 miles from their loft.
All but one of the birds with the severed trigeminal nerve were home the next day, suggesting that the ability to detect magnetic fields is not used to navigate. Among the control group, only one pigeon was lost.
Meanwhile, most of the birds deprived of their sense of smell got totally lost. Only four made it home.
