Karen and Alan Stockton hadn't expected the huge orange bill of a toucan grande to come quite so close. Or to spot the fearless great dusky swifts that dive through Iguazu Falls to nest on the cliffs behind.

"Toucans can be hard to see," Alan Stockton said. "We were lucky; we saw two different species (in a short span of time) — one landing on a branch directly ahead. It kind of stared down at us just as we were looking up at it."

Tropical birds are prolific in Argentina's Iguazu Falls National Park, but they're only one act of nature's spectacular show in the preserve, which is partly in Brazil. There, where South America's immense falls straddle the border with Argentina, a high-rising mist has created a semitropical haven for birds, butterflies, big cats, giant anteaters, monkeys and hundreds of orchid species.

As a stop on the way home to Honolulu from a scientific meeting in La Serena, Chile, the Stocktons' side trip to Iguazu was a natural. Both are keen birders and nature enthusiasts who excel at photography; natural beauty and wildlife take priority wherever they travel. "Even in big cities like New York, for example, there are places to find birds and parks with wildlife," said Karen Stockton. But no place is quite like Iguazu.

"(It's) stunning," Karen said, "We'd heard people talk about going there and its reputation as one of the main sights to see in South America, but didn't expect it to be so spectacular ... so abundant in birds and butterflies."

And water. Iguazu's 275 individual cascades stretch more than 1.5 miles along a rim shared by the two countries. Although the Argentine side has the best and most varied close-up views of the falls, the Brazilian side boasts the best panoramic view. Some cascades plunge 270 feet, (the height of a 24-story building); most are about 210 feet.

The epicenter of the falls is the Garganta del Diablo, or Devil's Throat, a semicircle of foaming violence plunging 250 feet into the Iguazu Gorge. Rainbows shimmer through the vapor, and the deafening roar can be heard for miles.

Whichever side of the falls you visit — and both sides are thrilling, said the Stocktons — a drenching, exhilarating experience awaits.

IGUAZU FALLS HAS IT ALL: STUNNING SCENERY, ABUNDANT TROPICAL WILDLIFE

Here's a quintet of things to expect in Iguazu Falls National Park in Argentina.

1. WILDLIFE

In a world coming to terms with the "inconvenient truth" of our footprint on the planet, Iguazu's huge expanse of jungle shelters the greatest biodiversity in Argentina. There are more than 450 species of birds, 250 different butterflies, 130 animal species, ferns, bamboo, orchids, bromeliads, begonias, azaleas and more than 120 tree varieties, the higher ones home to vividly plumed macaws and parrots. Pumas, jaguars and snakes live in the more remote parts of the forest but generally avoid human contact.

Getting close enough to photograph the beautiful wings of an ochenta (Spanish for 80) butterfly, delighted Honolulan Alan Stockton, who visited recently with his wife, Karen. Capturing the great dusky swifts dive-bombing Iguazu Falls proved a greater challenge.

"For every snap in which a bird appears, I have 10 empty frames," Stockton said.

2. FOREST TRAILS

Iguazu's high rainfall (80 inches annually) and subtropical temperatures have nurtured a dense rain forest, its canopy 90 feet above the forest floor, part of which makes up the Parque Nacional Iguazu shared by Brazil and Argentina. On the Argentine side, Sendero Verde is a 20-minute forest walk leading to a small wetland home of birds and butterflies. The two-mile Sendero Macuco trail, where the toucans steal the show, leads to a small waterfall. "As much as we enjoyed the falls, we also enjoyed walking these nature trails," said Karen Stockton. The couple walked with a personal guide at times, but also alone ... well, almost — sociable tufted capuchin monkeys and scores of iguanas kept close company.

3. IGUAZU FALLS

Iguazu, meaning Great Water, belongs to the gang of four greatest waterfalls in the world (alongside Niagara Falls on the U.S.-Canada border, Victoria Falls between Zambia and Zimbabwe, and Angel Falls in Venezuela). A UNESCO World Heritage site since 1986, the falls are accessible from both Brazil and Argentina. Visitors on the Argentine side traditionally walk along three major circuits on mostly paved trails leading to the best (and wettest) overlooks. An upper path offers the best panoramic view of the falls, while a lower path leads to individual falls. A narrow-gauge railway, Tren de la Selva, takes visitors to a trailhead overlooking the Garganta del Diablo or Devil's Throat.

Recognized as the world's mightiest single waterfall in terms of water volume, Throat was the location for the opening scene of the 1986 movie "The Mission," starring Robert De Niro and Jeremy Irons, in which a priest strapped to a board was dispatched over the falls to certain death. On the Brazil side, there is a trail and viewing platform that gives visitors the best panoramic view of all 275 falls that make up Iguazu.

Which side to visit? "See both," the Stocktons advised.

4. HUMMINGBIRD GARDEN

On the Argentine side in central Puerto Iguazu, the Hummingbird Garden is the backyard creation of the Castillo family. Year-round blossoming plants and hummingbird feeders attract more than a dozen species, depending on the season. Named for the hovering noise made by their wings, which flap up to 80 times per second in some species, the hummingbird is able fly backward or vertically while feeding.

"The garden is wonderful, very low-key," said Karen Stockton. "It was magical to watch such tiny creatures zip to and fro, and a photographer's paradise."

For a small entrance fee, visitors see up to 16 species of hummingbirds, depending on the season, along with bananaquits, tanagers and blackbirds. The owner is on hand to share information and help visitors identify the birds.

5. ITAIPU DAM

Nine miles upriver from Iguazu Falls is the Itaipu Dam, the world's largest hydroelectric project.

The enormous dam, completed in 1991, stretches five miles along the Brazil-Paraguay border and is more than twice the height of Iguazu Falls. Itaipu provides 25 percent of Brazil's energy supply and 78 percent of the energy for neighboring Paraguay.

Engineers had to shift the course of the seventh-largest river in the world, the Parana, around the construction site before building the dam. Fifty million tons of earth and rock were removed in the process. The American Society of Civil Engineers recognized this amazing feat and named the Itaipu Dam one of its "Seven Wonders of the Modern World."

Free guided tours are daily except Sundays. "Book an English-speaking tour that goes inside the dam so you get to see the giant machinery," said Karen Stockton. "In one place, you can stand at the point where Brazil, Argentina and Paraguay meet."

Reach Chris Oliver at coliver@honoluluadvertiser.com.