Female birds can become sexual showoffs

ITHACA, N.Y., Dec. 15 (UPI) -- Cornell University scientists say they've discovered female birds in species that breed in groups can evolve the same kinds of sexual embellishments as males.

The researchers said such female birds become "sexual showoffs," evolving fanciful tail feathers or chest-puffing courtship dances, as do males.

"We've known it happens with females in some specialized cases, but it's probably more widespread than we ever realized before," said Assistant Professor Irby Lovette, co-author of the study with Assistant Professor Dustin Rubenstein, now at Columbia University.

The researchers said they found sexual selection is strongest in situations where not every individual gets a chance to reproduce. Called reproductive skew, the pattern tends to be common in males. Females of most species generally invest more in producing and nurturing young and tend to have more steady reproductive success.

Rubenstein and Lovette reasoned that if sexual selection were to operate on females, it would likely be in situations where females had to compete for mates. They found among pair-breeders, sexual selection on males makes the sexes look increasingly different. But in cooperative breeders, competition among females leads to them evolving the same showy traits as males.

The finding that reproductive skew dictates how sexual selection acts could apply to nearly any species that breeds in groups, the researchers believe.

The study appears in the journal Nature.