Call it the case of the "smoking duck."
One of the most difficult wildlife mystery stories ever to confront federal authorities has come to an end, a vivid but belatedly successful end, after perplexing for 10 years.
"Why are the birds dying?" "What's killing the birds?" ask headlines that have appeared here since 1981.
That was when hunters began to report significant numbers of dead waterfowl in the marshland next to the artillery impact range at Ft. Richardson Army Base. Since 1961, the base has maintained an artillery range in the wetlands, near Anchorage.
You amateur sleuths figured it out already, huh? Ducks fly to the wetlands. The Army opens fire. Dead ducks.
If only it were so simple.
Biologists began investigating in the Eagle Flat estuary and quickly discovered that birds did not seem to be dying from shrapnel or concussion.
Much of the firing range was unapproachable, off limits because of unexploded ordnance. By traveling around the edges, biologists found 368 dead ducks in 1983, and 198 more the next year. A limited effort in 1985 found nearly 100 bird carcasses, including a bald eagle and five swans.
Biologists noted that the bodies were not found in clusters but seemed to be distributed randomly. Initial lab testing indicated that the birds had succumbed quickly, thus probably not because of an accumulation of heavy-metal or pesticide poisons. There was no evidence of infectious disease.
A memo written at the time concluded that the Eagle Flats wetlands were contaminated with toxic chemicals, perhaps as a result of artillery firing.
Officials can now say the findings should have spurred on the probe. But the work sputtered and languished.
In 1987, wildlife agencies and the military joined to explore the problem.
For two years, they marked carcasses, studied upstream water for contamination, analyzed soil samples. Again, no headway.
By this time, researchers believed that they had eliminated such possible sources of contamination as upstream sewage or old gold-mine tailings from a river that fed the wetlands.
Public interest and concern grew over the years. "Still no answers," one headline said. The Army ceased firing on the range. Attention focused on munitions residue in the soil.
"The Army made this stuff to blow things up. There were no studies of these materials as contaminants. That was our problem," U.S. Fish and Wildlife Service spokesman Bruce Batten says.
In 1990, researchers placed "sentinel" birds in cages in the wetlands. Automatic cameras videotaped them eating and living in the environment. Researchers began to see hideous sights: Healthy birds would suddenly lapse into convulsions and die in agony.
Something deadly was down in the bottom of the marsh. But what?
It eluded the efforts of scientists until a few months ago. Then, a researcher from the Army's Cold Regions Research and Engineering Laboratory was preparing a duck carcass for analysis. When she cut into the dead animal's gizzard, she noticed it began smoking ever so slightly, a distinct white smoke that smelled of garlic.
Because of her Army training, she knew it was white phosphorous.
Known as WP, or Willy Peter, white phosphorus burns spontaneously when exposed to air. It ceases to burn when smothered, such as with mud, but then ignites again in air. WP is commonly used in artillery shells and mortars to create smoke screens.
Researchers concluded that the ducks had been eating small bits of residual white phosphorus and dying of a poison that left no evidence. The actual cause of death was a toxic reaction to the WP, not burns. But the evidence simply fizzled away whenever scientists prepared a soil sample or duck carcass for study.
Mystery writers had been searching their imaginations for generations for just such a thing.
Since then, the Army has ordered a halt to the firing of white phosphorus at all its artillery ranges around the country where there are wetlands. The tally of dead birds at Ft. Richardson is now in the thousands. And the cleanup is only now being studied.