For the birds: Whether you're territorial, a girlfriend stealer or a cross dresser, it's in your genes

Individual animals usually exhibit flexibility in their behaviour, but some behaviours are genetically determined.

Using genome sequencing, researchers from the University of Sheffield have now identified the genes that determine the striking mating behaviour of the males of a wading bird known as the ruff.

The ruff has a 'lek' mating system, which means males of the species gather together and invest all of their energy into attracting females to mate with them, and none into parental care.

Within this specific mating system three distinct breeding behaviour types are easily identifiable.

• Territorial breeding males have spectacular plumes around their neck (which is why these birds are called ruffs) and head, and vary enormously in colouration so that each male is distinguishable.

• Nonterritorial so-called 'satellite' males, which are distinguishable by their white feathers, concentrate on stealing mates from the territorial displaying males.

• A third type of male, which is thought of as a 'cross-dresser', mimics females. They are able to hide from other males in the lek, so avoiding territorial aggression, and succeed by effectively stealing mates from the resident males.

The new study, by an international team including researchers from the University of Sheffield, Simon Fraser University (Canada), and the University of Edinburgh, published in Nature Genetics, shows that the three distinct breeding behaviour types are encoded by a 'supergene' -- a section of a chromosome containing a hundred or more genes.

This supergene was created several million years ago by a chromosomal rearrangement, which originally allowed the female mimic to evolve and coexist with the territorial males.

Lead author of the study, Professor Terry Burke from the University's Department of Animal and Plant Sciences, said: "The special feature of the supergene is that it allows lots of genes that are next to each other on a chromosome -- which in this case determine multiple traits including hormones, feathering, colour and size -- to evolve together and create two distinct behavioural traits.

"This process is similar to the one that led to the evolution of separate sex chromosomes, and indeed the alternative forms of the supergene combined together to create the third type of bird personality -- the girlfriend stealer.

"The ruffs provide a neat example of how small genetic changes can lead to major differences in attractiveness and behaviour. This process is fundamental to the formation of separate sexes and separate species."

He added: "Unlike young men at a social occasion who have each chosen a different approach to courtship, whether that's showing off or paying a compliment, for these birds there is no choice in the matter. It's their DNA that dictates how they win a partner."