The temptation to see parallels between the behavior of Molothrus ater (brown-headed cowbird) and Homo sapiens can be irresistible for some of us. White has a slightly different perspective.
“Us animal behavioristswe’re a weird group,” he says. “We really don’t look for the human connection as much as many people would expect us to. I think we look at humans and think about how cowbird-like some can be.” On the other hand, “there have been males and females long before there have been humans. So it stands to reason that there are going to be some generalities there.”
One is “this idea of the females coming in and being interested in the males, and all of a sudden stimulating the males’ aggressive behavioryou see that in humans all the time,” he allows. “Once a female’s involved, the rules of the game change no matter what game it may be.”
An old Jimmy Reed song comes to mind: “I’ll Change My Style.” If memory serves, it includes the line: “And if my lovin’ don’t please you,/ I’ll change that too.” It could be the theme song of the lovelorn male cowbird.
“Males are much more malleable than females,” says White, who has Buju Banton’s “Circumstances Made Me What I Am” playing on his mental iPod. “We had an experiment where we kept putting in males with interested females and changed the males, but as you moved the females around they didn’t change all that much. So they were the ones changing the males.”
There may be aspects of female behavior that are as malleable as their male counterparts’, he acknowledges. “We just don’t know how to find them. Right now, I don’t understand female cowbirds, frankly. Males are pretty much an open book, easy to read. Females are just tough. It’s all because of this subtle behavior. Males will tell you exactly how they’re feeling: big song, big display. The females stepping half an inch one waythat’s a big signal for them.”
Say you’re a stranger in town, and you have a foreign accent. For a man hoping to get lucky, that might or might not be a handicap. For cowbirds, it’s pretty much: Talk like the locals, or go home alone.
“Females have their preferences,” says White. “They have their song and the male has to fit that song to that preference.” His former colleagues at Indiana found this out unexpectedly, he explains. They put an Indiana male in with a female from Oklahoma, and assumed that, with time, the female would develop a preference for Indiana song.
“The experiment in that way was a spectacular failure, because by the end, all the males have Oklahoma song,” says White. “They change their song to be the variant for the female. The social-conformist male does whatever he has to do to make this female happy.” By such failures does science advance.
The male’s education, it turns out, hinges on a tiny movement of the female’s wing known as the wing-stroke. West and King soon determined that the male was changing his tune, but couldn’t figure out what was prompting him to change it. So they watched the interactions between the male and the female in slow motion, frame by frame.
“That’s the only way you can see this behavior,” says White, “but the behavior is a wing-stroke, and it’s a little 200-millisecond movement of the female’s wing in response to a song. And it’s very interesting to the male.
“It could be that this is the way females are actually selecting a male,” he adds. “They’re selecting an attentive, good male that can read a female.”
The equivalent of a good listener? “Exactly. And this is why females generally stay away from juvenile malesthey’re as likely to peck at you or jump on you as to sing to you. And that typically is a big turnoff to females.” Adult males, or the more perceptive juveniles, will “take a little step, give a little whistle, give a little song, take a little step, and eventually get right in close.”
And that’s where the real action is. “The song of the male is fundamentally different hearing it at one foot versus anywhere greater than one foot,” White explains. “The sound and the notes attenuate very dramatically, and you have to be very close to the female to get her to go into the posture. Because it’s those first notes that really stimulate her to go into that posture.
“So for a male, he’s got to learn that if he wants to get copulation, he’s got to get very close to the female. That’s a simple thing, but it was really hard to realize because what you’re measuring there is the absence of behavior of the female. Females sitting there looking bored is a huge cue to these males.”
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©2005 The Pennsylvania Gazette
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COVER STORY: The Cowbird Variations