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Be My Scientific Valentine
  1. A day for lovers

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3. Canadian Diamonds

4. Bird mating: She rules!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  head of male bower bird Like that strong sensitive type?
If you missed the Super Bowl and all those SUV ads, the term "male display" might have little meaning. But ecologists and evolutionists say these displays are designed to seduce a female for mating purposes.

Translated, displays help pass along the genes.

Seems to us that only the seagull or gorilla or barfly that is the lucky target of the male display can know the exact message. But in general, male displays include:

I've got energy to help raise the young 'uns.

None of the other guys would dare mess with me -- or my kids.

I'm a man (or one spanking fine bird).

I've got dynamite genes.

I'm healthy.

Male displays often involve a tad of male-bashing -- as mule deer crash heads or walruses whonk tusks. But like guys duking it out in a roadhouse parking lot, the displays can get a bit intimidating to the ladies who are their supposed beneficiaries.

You don't have to be a feminist (although it might help) to wonder: Is this what the ladies really want? Or do aggressive mating displays frighten the females instead of impressing them?

The question reflects a change in focus of evolutionary theory. Until recently, biologists who studied mating behavior focused on males. Lately, they've begun to wonder about "female choice." Are the ladies actively choosing males during courtship? If so, what do they make of male behavior?

Graph on left shows courtship success rises with male display intensity. Graph on right  shows courtship success dropping when female is startled.
(Left) The more intense the display, the more likely a male is to mate with the female he's attracting. (Right) The more a guy startles the female bowerbird, the less likely he is to mate with her. Courtesy Gail Patricelli

Take a bow, bowerbird
University of Maryland biology doctoral student Gail Patricelli has taken this question one step further in her study of the bizarre courting behavior of the satin bowerbird. People who watched Ptilonorhynchus violaceus have begun to wonder about a really ridiculous question: Does female behavior influence male behavior during courtship?

In other words, do the two sexes communicate at this crucial moment?

We'll get back to that heretical notion shortly. First, we need to backtrack for some background.

Shiny blue-black bird standing near tree, resembling a crow.Male Satin Bowerbird.Courtesy (c) Grover Larkin.

If you're into animal courtship, you probably know the little bowerbird, a native of Australia and New Guinea. The males build elaborate "bowers," or courting courtyards, which Patricelli describes as "a two-walled stick structure with a platform, decorated with different colored objects."

But not just any color, she adds. "Bright blue is a favorite color for satin bowerbirds. They'll use parrot feathers, but if people are around they will use pen caps or shotgun shells. My favorite was a baby pacifier."

During mating season, in the spring, the ladies tour the bowers, sizing up the studs by their architectural prowess and by their talent at staging "a dramatic, coordinated display of feather-pulling, extending the wings suddenly, and running accompanied by a loud buzzing vocalization," Patricelli and Gerald Borgia wrote (see "Male Displays..." in the bibliography).

Too much of a good thing?
Gerald Borgia, a University of Maryland biology professor who has studied bowerbirds for 22 years, found that an intense and aggressive display is essential for mating success. He says most males do not score, but the winners get multiple partners, and the chance to pass their genes to the next generation. "One very successful male who had a good bower mated with 25 females over one 2-month mating period," said Borgia. "The sexiest guys get all the mates."

But what is sexy? Patricelli says females may be startled (looking like a 7-year-old who's seen a ghost) when the guy gets too hot and heavy. That's logical, since the mating dance resembles what the male uses to intimidate other dudes at feeding sites.

That, says Patricelli, cuts into the romantic effect and damages the guy's chances of scoring.

So with bowerbirds, as with Homo sapiens, smart fellas are cautious fellas during courting. "They need to be very aggressive during courtship, but the female can be threatened," says Patricelli about the birds. "It's a delicate line. They've got to be intense, but if they're too intense at the wrong time, it can scare her off."

(Sound familiar, guys?)

In other words, females can get frightened when the bowerbird goes overbird -- we mean overboard.

movie image of male strutting in front of robotic decoyThis 596k movie shows the male satin bowerbird trying to mate with the decoy robotic female.
Courtesy University of Maryland.

Fembot Schlembot
To test whether successful guys -- the ones that can convince females to mate -- are taking cues from the gals, Patricelli and Borgia collaborated with Gregory Walsh, a mechanical engineer at Maryland, to build a robot female that could dance, weave and crouch like a real, live female. Once the robotic "guts" arrived in Australia, Patricelli dressed it in a real bowerbird feather suit.

Call it robotic taxidermy in the service of science. Over at Borgia's lab, they call it "fembot."

Whatever.

The ability to crouch is critical because it's how females signal that they are comfortable with the intense, aggressive displays. The fembots were so realistic, said Walsh, that two male bowerbirds fought for the right to mate with a fembot (if that is not against the law in Australia, it ought to be).

By testing males with robotic females, Patricelli and her co-authors were able to show that the most successful males were those that gave highly intense displays without threatening females, and that they succeed in mating by modulating their displays in response to female crouching signals. "The most attractive males are those that have it [the heavy display] and know how to use it," says Patricelli.

Gold and green female in grass. Brilliant blue eye visible with bird standing in profile. Female Satin Bowerbird.
Courtesy (c)Grover Larkin.

Communication: The key to true love?
Before you start picturing male bowerbirds as paragons of peace who soothe females by cooing the avian equivalent of "Thank you for sharing that...", remember that the guys are nasty to their buddies. During the two-month mating season, Patricelli says, the males "defend against rival males, destroy each others bowers, steal decorations...."

Far from "love thy neighbor," we're thinking, "Blast that bloke, Bud!"

Nor are these ideal mates from the female's point of view. For all the effort male bowerbirds pay to attracting females, they pull an immediate fade-out after scoring. Males, says Patricelli, "don't provide any parental care, so they can dedicate themselves entirely to mating."

Ladies: Remind you of anyone you know?

Our bibliography will remind you of nothing under the sun.

 

 

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