Walker noted that clay licks in the Amazon River Basin are a particular draw. Hundreds of macaws and parrots gather at the exposed riverbanks to feed on clay, which helps the birds digest their diet of nutritious seeds.
Valqui, the LSU graduate student, said another great spectacle is the mixed flocks of birds, composed of as many as 70 different species, that can be seen swooping through Peru's rain forest.
"Each species is represented by a pair of birds, and maybe a young or two, moving through the forest, each one with a specific role," he said.
Sentinels in the flocks keep one eye out for the approach of predatory birds such as forest falcons or hawks. The guard birds also watch for large insects, which the flock sends scampering for cover. Other birds hunt insects as they scurry from niches in the rain forest canopy.
Biologists believe the advantage birds gain by foraging in a mixed flock is primarily one of protection against predators. Also, since only one pair of each species is allowed to join the flock and each species is a niche forager, competition is kept to a minimum, Valqui said.
The flocks themselves are territorial. When two mixed flocks cross paths, bird-watchers are witnesses to elaborate, complex screaming matches between like species in each flock.
"Regarding bird-watching, it's known to be feast or famine," Valqui said. "You can be walking in total silence, and you think, What's going on here? They told me the tropical rain forest is full of birds; they were talking about 20 to 30 species in a flock. When the flock arrives, it is actually too much."
Valqui, whose guidebook Where to Watch Birds in Peru was published in August, added that birders quickly learn to cope with the diversity.
"I have guided several tourists in Peru who see more birds in a week or even a day than they saw in their homeland in the last five years," he said.
Schulenberg, the Field Museum conservation ecologist, noted that there are some bird species that can only be seen in Peru. He added: "There are any number of spectacular individual birds, such as the Andean condor and Andean cock-of-the-rock, that are found as easily in Peru as anywhere else."
The Andean condor, one of the world's largest flying birds, soars on ten-foot (three-meter) wingspans and can weigh up to 33 pounds (15 kilograms). The Andean cock-of-the-rock is a brilliantly colored, pigeon-size bird known for its elaborate courtship displays.
O'Neill, meanwhile, said he is thrilled at what he describes as surging interest in Peru's birds. Working with colleagues, O'Neill is preparing a field guide to the country's birds to be published next year.
"When I first went to Peru in '61, I knew of two or three people interested in birds. Last October there was a Peruvian workshop on ornithology in Arequipaa city in the southand there were 350 to 400 people there," he said.
While the workshop drew an international audience, O'Neill estimates 250 of those who attended were Peruvian, many of them college-age students pursuing science careers.
Valqui agrees that interest in Peru's birds is growing but cautions that the bird-watching industry is still young.
"It has changed from zero to a little bit, and that might be a big step," he said. "Maybe the toughest step has been done."
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