Air Date: Week of April 11, 2003

Living on Earth’s Cynthia Graber reports on a new study showing why male birds with brighter beaks get more girlfriends.

Transcript

CURWOOD: Coming up, a fight over grazing rights on historically Native American land. First this note on Emerging Science from Cynthia Graber.

[MUSIC: Science Note Theme]

GRABER: Some male animals go to extremes to attract a mate. They may perform an elaborate courtship dance. Others sing. And still other attract their partners by the color of their beaks.

Scientists have suspected that the brightness of a bird's beak was related to its health. Now, a new study published in the journal Science demonstrates that the brighter the beak, the stronger the male's immune system.

Scientists in the UK added chemicals called carotenoids to the water of ten zebra finches. By doing this, researchers were hoping to stimulate the birds' immune system. Carotenoids are found in many vegetables, and have been linked to disease resistance.

Scientists then measured the strength of the birds' immune system by injecting them with a protein that causes swelling. Compared to birds who did not receive the supplement, the carotenoid-strengthened birds were better able to fight off the protein. And those same birds also developed brighter red beaks. What's more, in nine out of ten cases, female birds preferred these males over the drabber ones. This is the first time scientists have shown strong evidence that beak color is directly related to immune strength.

So when females go for the most flashy suitor, they're not being shallow. They're just choosing a healthy mate. That's this week's not on Emerging Science. I'm Cynthia Graber.

[MUSIC]

CURWOOD: And you're listening to Living on Earth.

[MUSIC: Pat Metheny “Airstream” American Garage ECM (1979)]

CURWOOD: It's Living on Earth. I'm Steve Curwood.

MUSIC: [Kronos Quartet “Foday Musa Suso” - Pieces of Africa Elektra (1992)]

CURWOOD: A good time of day to go looking for wildlife in Africa is that moment when daylight slips into darkness, the moment when hunters and the hunted begin to play their game.

Recently on safari in the Kruger National Park, I got in a Land Rover for a sunset drive and a chance to catch lions at work. There were plenty of antelope about, the always graceful impala in herds that seemed to turn as one, the kudu, big wishbone markers on their big sides. Surely, with so much to eat on the hoof, big cats would make a move. But as the sun slipped away there were no lions to be seen anywhere. And then, caught by a spotlight low in the grass, I saw them, a pride of eight or ten, looking rather lazy, sprawled about and not unlike housecats.

One lion was busy licking behind the ears of another, who sat with eyes blissfully closed as she enjoyed the massage of the rough tongue. She had to be purring, if lions purr, but I wasn't about to get close enough to find out. A couple of younger lions played a bit, but the pride was pretty quiet. Perhaps it was after dinner. We had missed the hunt, I guess, and perhaps that was a good thing. They wouldn’t be thinking about us for dinner in that case.

Thanks to Heritage Africa, you can travel to the great wildlife reserves of Africa and get a chance to see lions at home in the bush, perhaps grooming each other, or better yet, catching dinner. Living on Earth is giving away a 15 day trip for two on the ultimate African Safari, with visits to several wildlife hotspots, including Kruger and the Serengeti. Please go to our website – www.loe.org – for more details about how to win this 15 day trip to see some of Africa's most spectacular sites. That's loe.org.