Birders flock to rugged and remote Palo Verde, a marvellous repository of avian fauna at the mouth of the Rio Tempisque, named for the green-barked palo verde, or horseshoe bean tree. Combining wet and dry ecosystems, it supports not only vast flocks of waterfowl but crocodiles and mammals that are easily seen in the sparse vegetation.

The 13,266 ha park encompasses 15 distinct habitats from mangroves, grassland, and scrubland, to tropical dry forest. This oasis in the heart of the rain-starved Tempisque Basin is fed by the Rio Tempisque and its mangrove-lined tributaries, forming an aquatic haven for birds- more than 300 species of new-tropical birds roost or nest here.