About 30km west of Cañas on the northern bank of the Río Tempisque lies the PARQUE NACIONAL PALO VERDE (daily 8am–5pm; $10), created in 1982 to preserve the habitat of the migratory birds that nest in the estuary of the Tempisque and a large patch of relatively undisturbed lowland dry forest. With a distinctive topography featuring ridged limestone hills – unique to this part of the country, and attesting to the fact that certain parts of Guanacaste were once under water – the park shelters about fifteen separate ecological habitats. From December to May, Palo Verde can dry out into baked mud flats, while in the wet season, extensive flooding gives rise to saltwater and freshwater lakes and swamps. Following the wet season, the great floodplain drains slowly, creating marshes, mangroves and other habitats favoured by migratory birds. Little visited by tourists, the park is mainly of interest to serious birders, but what you see depends on the time of year – by far the best months are at the height of the dry season (Jan–March), when most of the 250 or so migratory species are in residence. In the wet season, flooding makes parts of the park inaccessible.
The park is home to one of the largest concentrations of waterfowl in Central America, both indigenous and migratory, with more than three hundred species of birds, among them the endangered Jabirú stork and black-crowned night heron. Further from the riverbank, in the tree cover along the bottom and ridges of the limestone hills, you may spot toucans, and perhaps even one of the increasingly rare scarlet macaws. At evening during the dry season, many birds and other species – monkeys, coatis and even deer – congregate around the few remaining waterholes; bring binoculars and a torch. Note, though, that you shouldn’t swim in the Río Tempisque (or anywhere else), as it’s home to particularly huge crocodiles – some, according to the park rangers, are as much as 5m long.