Equally surprising to researchers, the toxin in the pitohui has been seen nowhere else in nature except in the poison-dart frog, a South American amphibian and the source of the toxin that many Amazonian hunters use on the tips of their blow-darts. That two such wildly different animals, a bird and a frog, living so far apart independently evolved an identical chemical defense mechanism is a completely unexpected finding. The poison, called homobatrachotoxin, is one of the most lethal toxins ever discovered.

"It was amazing when we isolated this substance and realized what it was," said Dr. John W. Daly of the Laboratory of Bio-organic Chemistry at the National Institutes of Health in Bethesda, Md., who performed the chemical analysis of the bird poison. "The compound is hundreds of times more toxic than strychnine."

The substance acts as a neurotoxin, disrupting the sodium balance in nerve cells and causing muscles to contract uncontrollably. Among the many mysteries that scientists must now explore is why the pitohui does not itself suffer any ill effects of carrying around the neurotoxin, a puzzle that they have yet to explain for the poison-dart frog.

John P. Dumbacher, a graduate student at the University of Chicago who worked with Dr. Beehler, made the discovery incidentally while studying birds of paradise in the New Guinea rain forest. The pitohuis often became entangled in the nets set out for the birds of paradise, and Mr. Dumbacher, while trying to free the intruders, would cut his hands. Upon licking his wounds, Mr. Dumbacher found that his mouth began to tingle, burn and turn numb. 'Use All Your Senses'

"In third grade they tell you to use all your senses to study nature," said Mr. Dumbacher. "We were moving so quickly from net to net that we ended up doing exactly that."

After consulting with local New Guineans, Mr. Dumbacher and others on the team learned that the villagers knew hooded pitohuis as "rubbish birds," not to be eaten unless skinned and specially prepared. As it turned out, the parts of the bird the New Guineans refused to eat were just those parts that contained the neurotoxin.

"They're completely familiar with their land," said Mr. Dumbacher. "They know every tree, every bird, every species in the forest." Not surprisingly, Mr. Dumbacher has abandoned the bird of paradise and instead made the hooded pitohui the subject of his doctoral dissertation. Among the questions he will seek to answer is where the bird gets its poison, and whether it synthesizes it entirely on its own or relies on insects or plants in its diet to provide the molecular precursors.