Guayabo, Negritos and los Pájaros Islands, scattered over Nicoya Gulf, were declared biological reserves to conserve the population of seabirds and the nesting sites of the brown pelican.
Los Pájaros is an islet of 3,8 hectares composed of Tertiary sedimentary rock. It rises 45 meters high and is connected to the shore by rocky platforms that are visible at low tide. It stand 500 meters off the eastern coast of the gulf basin, forming part of a very hot and dry climate zone. As a result, the plant species that grow on the islet are deciduous and semi-deciduous, such as the wild guava, stinking toe, wild fig, ear tree and manteco, interspersed with secondary growth. Due to its proximity to Costa de Pájaros (Bird Coast). the islet is frequented by an infinite number of seabirds, mainly brown pelicans.