The Sexiness of Clueless Males
Male cowbirds raised without access to other birds develop their own peculiar version of a cowbird song. Strangely, females love these untutored songs, showing twice as much sexual interest as they do for the songs of normal males from their own population, according to research in the 1970s and '80s by Meredith West and Andrew King. And it's not just a matter of females liking novelty, because female cowbirds don't like the accents of wild males from distant locations. Instead, the naive males' songs seemed to have particular acoustic features that made them attractive.
But in cowbird society, it's not enough merely to be attractive to females. A male also has to earn social dominance and acceptance. When King and West placed formerly isolated males in aviaries with wild-caught cowbirds, the wild males attacked and often killed the naive males as soon as they tried to sing.
"These [isolated] males could put any female into a copulation solicitation display with their song," said White, who has studied cowbirds with King and West. "[But] males respond really aggressively to a really good song, and these poor little guys get beaten up by the other males and they never actually get to reproduce."
This apparent paradox makes sense when you realize that in cowbird groups, dominant males sing more attractive songs than males ranked lower on the pecking order. When these dominant males are moved into new groups where they no longer hold high rank, they are often attacked and killed. White believes that for females, the songs serve as an honest signal of mate quality, since only high-ranking males can get away with singing attractive songs. The best song for a male to sing depends on the expectations of other males in his population, so it's important for him to be able to learn from the right birds.