Home to well over three hundred species of bird and a mindblowing variety of reptiles and mammals, the Esteros del Iberá are a paradise for any visitor with an interest in animals. Armed with binoculars and a guidebook to South American species, you stand an excellent chance of observing dozens of different varieties in just an hour or two; a good guide will help, too.
A common sight and sound around the Laguna del Iberá are chajás (Southern screamers), large grey birds with a patch of red around the eyes and a look of bashful nervousness. They frequently perch on the trees on the lakeside, nonchalantly chanting “aha-aha” but occasionally emitting a piercing yelp (hence the English name) similar to the sound a dog makes when trodden on. Other large birds include sleek, black Olivaceous cormorants; Maguari storks, with striking black and white plumage, and a tendency to soar on the thermals above the lake; and Striated herons, characterized by a black crown and a lazy disposition. A particularly impressive sight during the spring nesting period is that of the garzales, where hundreds of normally solitary herons unite in a spectacular mass gathering. Another magical, if rarer, sight is the elegant jabirú, a long-legged relative of the stork with a white body, bright crimson collar and a black head and beak. Different species of kingfisher also put on a show of aviation prowess, swooping across the water or diving into it. Wattled jacanas, on the other hand, prefer to scuttle over water lilies and floating weeds, seldom showing off their lemon-tipped wings. Another strange-moving bird is the Giant wood-Rail, or ipacaá, whose Guaraní name is onomatopoeic; it croaks plaintively as it tiptoes around near houses, grabbing any food left out for it and scampering off to peck away at it.
Reptiles and insects
Birds are not the only wonders around the esteros. Among the reed beds at the edges of the lake you may catch sight of large snakes, such as the handsome yellow anaconda, its golden skin dotted with black patches; they can reach up to 3m in length. As you approach the edges of the floating islands, in particular, charcoal-grey caymans, or yacarés, freeze, often with their ferocious-looking jaws stuck open, or else they suddenly slither into the water, where they observe you with only their eyes peeking above the surface. Another startling spectacle is provided by creepily large spiders, which lurk in huge webs among bushes and reeds, waiting for their helpless insect prey. Some guides delight in making it look as though the boat is heading straight for them, so arachnophobes be warned. Rather more appealing are the hundreds of butterflies, in every colour imaginable, an enchanting sight you will see all over the region.
Mammals are well represented, too. Howler monkeys – which really growl rather than howl – are much easier to hear than to see, but you might, if you are patient, observe their antics near the visitors’ centre or in other tall trees in the area. Listen, too, for the sudden splash of a capybara, or carpincho, diving into the water. On land, this guinea-pig-like mammal, the world’s largest rodent, looks almost ungainly, but they are incredibly graceful as they glide through the water. The floating islands are where the capybaras go to sleep and graze. There, and on the marshy lands and pastures around the more isolated extremes of the lake, you may also spot the rare marsh deer, South America’s largest, equally at home in the water and on dry land. If you approach them gently, these astonishingly beautiful animals seem to accept your presence and continue grazing lazily on aquatic plants. Rarest of all of the esteros’ wildlife, and certainly the hardest to spot, is the endangered aguara-guazú, or maned wolf, a reddish long-legged creature that awkwardly lopes through the vegetation, moving first its two left legs and then the two right ones – or so they say.