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The drama on Lake Aziscohos in western Maine last July began with an eerie midnight duet. From a small boat, biologist David C. Evers played a recording of the cry of a common loon. From the darkness came an answering wail. One of Evers' helpers stabbed the darkness with a searchlight. There! The loon was caught in the beam, head feathers shimmering. Little did it know that it would soon help biologists probe both the mysteries of loon behavior and questions about pollution from a toxic metal, mercury.IP2,0

Jeff Fair, an independent loon biologist, steered towards the curious bird. Dazzled by the spotlight, the loon couldn't see the scientists. With the boat just 2 feet away, the bird dived for safety--right into a net. The athletic Evers lifted his subject onto the boat. Fair wrapped its head in a towel, and Evers attached leg bands, snipped a few feathers and stretched out one short, muscular leg so colleague Erin Harshberger of Tufts University could draw blood. The samples would later be tested for mercury. Then Evers weighed the loon and lowered it back into lake.

Until Evers developed a twist on this capture technique in 1989, for the most part adult loons had eluded biologists trying to capture live birds for up-close study. Sure, their shoreline nests are simple to observe. So too are the birds' courtship dances and water-splashing territorial fights between males. And the birds' helplessness on land has long been well known: Loons need a take-off run of as much as a quarter-mile across open water. Many a loon has mistaken a rain-slicked road for a lake, crash- landed and been unable to get into the air again.

But scientists still can't determine the age of an individual bird; it's even hard to tell two birds apart. "Loons are great 'liars,'" says biologist Fair, who has studied them for 18 years. More than once, he has been convinced that a pair of loons has given up on nesting for the year-- only to spot the birds weeks later with a couple of chicks. Or a chick may seem to disappear. "You put a zero down in your notebook and feel forlorn," says Fair. "Next day, you look across the lake in the morning mist, and there is the chick."

# posted by Medical Information : 4:46 AM