The southern portion of South America plays an important role for the conservation of many waterfowl and waders. Migratory movements were, till recently, known only for Arctic or Patagonian species. The only exception was the Southern Pochard Netta peposaca, with a west—east winter migration from the lower Parana River valley to south Brazil coastal wetlands. The banding studies that have been conducted by the Centro de Pesquisas para a Conservação das Aves Silvestres (CEMAVE/IBAMA) since 1980, directly or through agreements with local organizations, showed more details of this migration, plus indications that other aquatic species such as Chilean Flamingo Phoenicopterus chilensis, other duck species, Neotropic Cormorant Phalacrocorax olivaceus and White-faced Plegadis chihi may follow the same pattern. A migration into the same area the Pantanal population of the Wood Stork Mycteria americana was only recently discovered, and other species may also do likewise when the Pantanal is seasonally flooded. The studies of such bird migration or movements between the main South American wetlands are of great importance to understanding their conservation needs, especially when international cooperation among the countries plays a most important role. The region has been suffering human pressures of various types, from land reclamation for pasture and/or agriculture to the operation, in the last 30 years, of big hydroelectric dams which affect the natural flow of rivers or keep flood-plains under water. The impending construction of the Hidrovia Paranà/Paraguay, a large project for heavy river use as a main transportation route, may represent an enormous impact on such rich aquatic habitats, demanding immediate cooperation among the countries involved to mitigate negative effects on the environment. The impact may be similar to what happened in the Mississippi valley early this century. The west-east movements between the Paranà River valley and south Brazil are of special conservation interest, as a nationally threatened species (in Brazil) is involved (the Chilean Flamingo) as well as duck species targeted for the hunting season in the area.