Storm petrel seabirds can smell their relatives
Seabirds are able to pick out their relatives from smell alone, according to scientists.
In a "recognition test", European storm petrels chose to avoid the scent of a relative in favour of approaching the smell of an unrelated bird.
The researchers think this behaviour prevents the birds from "accidentally inbreeding".
The study is the first evidence that birds are able to sniff out a suitable mate.
It is published in the journal Animal Behaviour.
Lead researcher Francesco Bonadonna, from the Centre of Functional and Evolutionary Ecology in Montpellier, France, told BBC Nature that the birds used smell to recognise and communicate their "genetic compatibility".
Sniffing out a genetically suitable mate is a well-known phenomenon in mammals. But until recently, scientists thought that birds relied on vision and sound when choosing a partner.
According to Dr Bonadonna, the fact that they use odours explains how these birds manage to return to their family colony to breed and avoid mating with a relative.
European storm petrels remain in the colony they are born in throughout their life, so this site is also home to several of their family members.
"These birds are [also] theoretically faithful to one mate for life," the researcher explained to BBC Nature.
"So a bad choice may have catastrophic consequences."
He said that smell or "chemical communication" was "the most ancient and simplest form of communication" in the animal kingdom, adding, "it makes sense that the birds would use it".
Birds that smell
Storm petrels are small nocturnal seabirds that breed in dark burrows or crevices.
One of the most striking features of these birds is that they smell - a warm, musky smell.
It is known that they find their food out on the ocean by means of a sophisticated olfactory ability (or sense of smell), so it isn't too surprising that they use this sense of smell in their social lives.
Many species of birds and other animals have ways of making sure they avoid mating with a relative: storm petrels do it by smell.
Tim Birkhead is the author of the book Bird Sense
To find out how much information the seabirds could gather from the scent of another individual, Dr Bonadonna and his colleagues collected bird scents by "taking swabs" from a selection of birds in their study colony.
The diminutive birds nest on a tiny island off the coast of Spain called Isla de Benidorm. Thanks to almost two decades of survey work on this particular colony, the scientists had a record of exactly which bird was related to which.
Once they had their scent swabs, the scientists set a group of petrels a test, placing one cotton swab with the scent of a relative on one arm of a Y-shaped maze and a swab containing the scent of an unrelated bird on the other.
Almost all of the birds that performed the test chose to walk along the arm containing the scent of the unrelated bird.
"This also ties in with the fact that, in 18 years of studying these birds, we have never found a related pair nesting together," Dr Bonadonna said.
Prof Rus Hoelzel from the University of Durham stressed how important kin recognition was for animals.
"There are various ways individuals may recognise kin, and [smell] has recently been found to be quite a common mechanism in mammals, but there had been little evidence for this in birds," he told BBC Nature.
"This study now provides some careful experimentation and good evidence [for it]."
Dr Bonadonna added that studying animal behaviour in detail was crucial in order to understand the consequences that human activity might have on them.
He added: "Our manipulation and pollution of the environment [and] even our 'blind' attempts to restore or preserve human-changed environments may have catastrophic consequences just because we do not have any idea of how animals may react."