Tuesday, 8 November 2011
Transvestite birds win competition for sex
In a species of hawk, males dress themselves up as females to gain a sneaky advantage in the mating game, according to a unusual study published Wednesday.
Most male marsh harriers (Circus aeruginosus) are grey, but more than a third have permanent plumage that mimics the colours of females, which are mainly brown with a white head and shoulders.
Seeking to understand the point of this cross-dressing, biologists probed the behaviour of harriers in the Marais de Brouage, a marshland in central-western France.
After identifying 36 breeding couples, they placed one of three types of decoys near each of their nesting sites: plastic figures that had been painted to look like a typical male, typical female or "female-like" male marsh harrier.
Typical males, defending their territory, were three times likelier to attack the typical male decoy than the other two decoy types.
What was even more striking was the behaviour of female-like males in breeding couples.
They played their fake female role to an extreme.
In a fit of jealousy, they were more than twice as likely to attack a female decoy than a male decoy.
Impressed, the researchers believe that the gender-bending hawks get a competitive advantage by mimicking females so thoroughly.