When R. Given Harper set out to understand why North America's migratory birds were declining, he set a unique course. While other researchers zeroed in on habitat loss as a key problem, he decided, on a hunch, to look at an old culprit - the pesticide DDT - and its specific effects on songbirds.
The results were intriguing. Traces of DDT and other related chemicals were showing up in the birds. But the real shock came when Dr. Harper, a biology professor at Illinois Wesleyan University in Bloomington, compared his results with DDT levels in nonmigrating songbirds. These year-round residents of North America - including a who's who of birds like the northern cardinal, black-capped chickadee, and dark-eyed junco - had more kinds of chemicals and dramatically higher levels of them than the migrating species.
Those are surprising results. Heavily restricted in the United States since 1972 and a declining problem for eagles, osprey, and other predatory birds, DDT continues to show up in alarming levels in nonmigrating songbirds. Does that spell trouble ahead for these still-healthy species? Are humans at risk? No one knows. But one lesson seems clear: Beware of what you put into the environment, because it can be extraordinarily difficult to remove.
"These [findings] are reminders that our decisions are going to affect us for decades," says Greg Butcher, a senior scientist with the Audubon Society and author of a recent "State of the Birds" report that showed many North American species in decline. "There may not be a toxic effect that kills birds at these levels. But it very well could affect their embryonic development."
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