POSTED 2 MAY 2002
The mating song of the black-capped chickadee helps females decide who's sexy, and who isn't. Courtesy National Park Service.
Sounds courtesy Daniel Mennill:
The best songs, it would seem, are about love. Whether it's a blues singer lamenting a lost love, or the sirens luring Odysseus to the shoals, a good song is a great way to attract the opposite sex.
This is not news to songbirds, who started mixing crooning and wooing long before Frank Sinatra lamented that he "didn't stand a ghost of a chance with you."
Songbirds
perform their vocal gymnastics to mark territory and get noticed by eligible
females. Many scientists think the quality of the song tells her about
his health -- since only a healthy guy bird could belt out the avian equivalent
of "Lover Man."
Now we hear that female black-capped chickadees do more than listen closely. When their fellas lose out in a song competition, the ladies respond.
But not with a soothing, "Honey, maybe you can't hit high C-sharp, but you're still number-one. Come kiss my chicken lips."
No. The takeaway message for the ladies is: "I married a loser!"
And then they step outside the nest for some quick action with another guy! In evolutionary terms, that would guarantee that at least some of her young get top-notch genes.
The day I lost my baby
This, in short, is the message of a new study by
Daniel Mennill and colleagues at Queen's University, Kingston, Ontario.
Mennill, a graduate student, is interested in how animals make decisions,
and especially how birds communicate during mating. Instead of looking
just at two parties, however, he's checking the network thing -- how,
say, a third party interprets communication between two others.
He calls it eavesdropping, since the females overhear the "conversations" of others.
Mennill studied wild-living black-capped chickadees at the Queen's University biological station and identified high- and low-status males. As with people, upper-crust chickadees skim off the cream, so to speak. "At a food source... everybody makes way for the highest ranking bird," he says.
Sing me softly of the blues
Male songs during mating season can be submissive
or aggressive, Mennill says. Aggressive
songs copy the pitch of the other guy's song.
In contrast, a submissive song uses a different pitch, giving the first songster some breathing room..
During mating season, Mennill hung out in the woods with a laptop and a speaker. He gathered the birds by playing the familiar chickadee call.
Bird
Blues
When the guys began their mating songs, Mennill used
software to identify the frequency, and then issued either an aggressive
or a submissive song from his laptop. Weeks later, after the young were
born, he took blood samples and used genetic techniques to determine each
kid's biological dad.
The genetics told the sordid tale, Mennill says. "After a high-ranking guy lost a competition because I matched and overlapped his song, his female engaged in extrapair copulations." To Mennill, this proves that the females are eavesdropping on the guy-to-guy discussion.
Although songbirds were once considered monogamous -- they hang out in couples, and all of the young in the nest of a dominant male are normally his -- their behavior actually has elements of Beach Blanket Bingo. Many females do a certain amount of stepping out on their mates.
So when the lady heard her guy humiliated by the computerized song, about half of her future young wound up having a different dad, Mennill reports. "She's accustomed to hearing him win every song contest, but after hearing him lose, she changes her reproductive strategy."
It's a lot stranger in the night
Indeed,
it took only six minutes a day, on two successive days, for the songs
to change the female's mind, says Mennill. Apparently "the kind of information
available through eavesdropping has a lot of importance relative to reproductive
strategies."
The overlapping and matching songs may have other uses, says Mennill. "Most animals, including chickadees, live in groups, where many males are singing at the same time. You have to have capacity to address one individual if you want to say 'Hey you, I want you out of my territory.'"
Moral of the story: Guys, if you want to impress the ladies, tune up those vocal cords,.
Karaoke, anyone?
-- David Tenenbaum
BIBLIOGRAPHY
Female Eavesdropping on Male song Contests in Songbirds, Daniel Mennill et al, Science, 3 May 2002.
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