Birds choose mates through 'sense of smell'

A new study has revealed that birds might choose their mating partners through odor.

The researchers from Konrad Lorenz Institute of Ethology at the Vetmeduni Vienna, compared the preen gland chemicals of black-legged kittiwakes with genes that play a role in immunity. Kittiwakes that smell similarly to each other also have similar genes for immunity. Since the birds prefer to mate with unrelated mates, the scientists have now found the likely mechanism by which they recognize relatedness.

More recently it has been shown that birds in several species also avoid breeding with MHC-similar mates. This poses a mystery. Whereas smell is a very well developed sense in mammals, it has long been thought that birds lack such keen olfactory abilities.

Although a growing body of research is showing that birds can discriminate odors more than previously thought, none had shown that birds can do as mammals and use odor to compare their MHC composition with that of prospective mates.

When birds groom themselves with their bills, they spread chemical compounds from their preen glands throughout their plumage. These chemicals produce odors that appear to be unique to each individual, providing an olfactory fingerprint. The team suspected that, just as in mammals, these odors may be used by kittiwakes to assess their relatedness to other individuals.

The new finding implied that individual kittiwakes that smell similarly to each other (i.e. have similar preen gland chemicals) also have similar MHC genes. Closer relatives therefore have more similar odors than distantly related individuals.

This suggested that birds might be able to compare their own odor with those of potential mates, and to choose unrelated individuals as breeding partners.

The new findings, moreover, open the door for further work linking mate choice and disease-resistance in birds.

The study is published in Nature's Scientific Reports.