Attention bachelorettes.
Want love? A mate? The happily ever after? Find yourself reading The Rules or trying eHarmony and 8minuteDating?
Perhaps you just need to take a cue from nature — Cassin’s finches to be exact.
It’s been well established that male Cassin’s finches — a redheaded songbird that breeds in the western United States — sing to attract females. So what can females do to increase their chances of being wooed?
Well, that’s not the question a team of biologists, including Carolina’s Keith Sockman, tried to answer when they started their latest study on the mating behaviors of Cassin’s finches. But that’s the question they came to answer after a series of experiments in which they took twenty wild finches — ten males and ten females — and housed them in separate cages in several single-sex chambers. They then recorded each male’s singing during two trials, each of which lasted two days: when the male could see and hear a female, and when he was isolated from females.
In the February 2005 issue of Biology Letters, the researchers report that males sang the most in response to the loss of a female, or prospective mate, but sang very little in the presence of a prospective mate or when males had not been exposed to females in several weeks.
So, as it turns out, “Males temper their efforts in attracting a mate depending on the likelihood of a payoff,” says Sockman, who conducted the study with biologists from the University of California at Davis and Johns Hopkins University.
But the story gets better.
Males’ efforts, or song output, varied depending on what Sockman calls reproductive competency. In bird speak, that means that attractiveness depends on how fertile the female is.
The males sang about three hundred songs an hour after the researchers took away the most fertile females, Sockman says, but the males sang about five or ten songs an hour after losing the least fertile females.
“They don’t just try to attract any female,” Sockman says. “As far we know this is the first evidence of male songbirds adjusting their mate-attraction efforts based on the presumed attractiveness of the female they’re trying to court.”
What’s most interesting, Sockman says, is that males were even able to determine which females were fertile. The researchers could determine which females were in their reproductive prime only after the fact, after females began molting, or shedding their feathers — a sign that breeding season is over.
“We are able to infer when females had peaked in reproductive competence relative to one another based on who began to molt first,” Sockman says. “Because onset of molt begins after reproductive competence ends, the males could not have used molt to gauge subtle differences between females in the reproductive competence.
“Thus,” he says, “males seem to cue in on something else.”
And though the researchers analyzed videotape recordings of the interaction between females and males, they could not detect any communication or behavioral differences during the interactions between fertile females and males and between less fertile females and males.
So, Sockman says, “It’s a mystery how the males can ascertain subtle variations in reproductive competence between females.” But, he says, the researchers know the males can ascertain female fertility “because of the variation in the rates of singing.”
Males also adjusted their song output in response to female availability, Sockman says. What did males do when females were in eyesight? The males sang very little.
“When there’s a female present, males don’t need to sing anymore,” Sockman says. “Some behavior can be costly for males, and singing takes time that can also be spent on other things such as feeding or protecting themselves from predators.”
So on the whole, Sockman says, when it comes to selecting a mate, males seem to be choosy.
“Ever since Charles Darwin, it’s been assumed females are choosier than males because females invest more in reproduction,” Sockman says. “Our research shows that males also can be choosy. It seems they choose who they are going to work the hardest to attract, presumably based on how attractive the female is.”
Can the same be said for human males? “I’m not sure our findings apply to humans,” Sockman says.
