The ability of pigeons to find their way home has fascinated people for millennia. Initially harnessing the birds to deliver correspondence, more recently people have raced pigeons competitively. But how do these remarkable aviators locate home after release in unfamiliar territory? Anna Gagliardo and her colleagues from the University of Trento, University of Pisa and Max Planck Institute for Ornithology explain that pigeons navigate using an olfactory map (p. 593). While sitting in their lofts, the birds are able to learn the directions from which odours originate and construct a map that is sufficiently accurate to guide them until they can switch to navigating by local landmarks. However, it seems that not all pigeon nostrils are equal: ‘The right and the left olfactory systems are not equally efficient in processing olfactory cues,’ says Gagliardo and adds, ‘Studies on pigeons released with one nostril occluded highlight an asymmetry in favour of the right nostril.’ Curious to find out how true this phenomenon is, Gagliardo plugged either the left or the right nostril of homing pigeons raised just outside Pisa and released the birds from Cigoli, 41.6 km away. Then the team tracked the birds' return routes with GPS to find out whether having a blocked nose affected their homing ability.

Analysing the flight paths of the birds, Gagliardo and her colleagues could see that pigeons that could not breathe through the right nostril took a more tortuous route, stopped more often and spent more time exploring stopover sites than birds that could breathe through the right nostril. The team suspects that the birds with blocked right nostrils spent more time exploring to gather additional navigational information and suggests that the left nostril is less sensitive to odours than the right. The team says, ‘The behaviour of the right nose plugged pigeons suggests a specific role of the right nostril in processing olfactory information useful for the operation phase of the navigational map.’

Olfactory lateralization in homing pigeons: a GPS study on birds released with unilateral olfactory inputs
J. Exp. Biol.