The largely pristine REFUGIO NACIONAL DE VIDA SILVESTRE CAÑO NEGRO, 25km southwest of Los Chiles, is one of the places in the Americas to view enormous concentrations of both migratory and indigenous birds, along with mammalian and reptilian river wildlife. Until recently, its isolation kept it well off the beaten tourist track, though access has improved and nowadays numerous tours are offered from San José, La Fortuna and – best of all – the adjacent village of Caño Negro.
The refuge is created by the seasonal flooding of the Río Frío, so depending on the time of year you may find yourself whizzing around a huge 800-hectare lagoon in a motorboat or walking along mud-caked riverbeds. There’s a 3m difference in the water level between the rainy season (May–Nov), when Caño Negro is at its fullest, and the dry season (Dec–April); while the mammalian population of the area stays more or less constant, the birds vary widely. The best time to visit is between January and March, when the most migratory species are in residence and you’ll see scores of caiman basking on the riverbanks.