Mar Chiquita is an extensive saline lake associated with the Dulce River marshes, which together form a wetland of about 1,000,000 ha in central Argentina. The lake has undergone marked fluctuations in surface area and salinity in recent decades, which has produced a marked effect on waterbirds. In the last decade, surface area and salinity of Mar Chiquita have changed little. However, there have been important changes in some species of waterbirds, particularly the Chilean Flamingo (Phoenicopterus chilensis) and the Wilson's Phalarope (Phalaropus tricolor). Also remarkable has been the appearance of eight species that inhabit marine coasts in South America, in addition to other seven coastal species previously recorded. In the present decade, Mar Chiquita has dropped 1.7 m, but for the moment this change has not had a major influence on waterbirds.