The proximity of the Tropic of Capricorn (which actually crosses parts of the country in the northwest), together with the topography and regional rain dynamics, provides optimal conditions for an array of subtropical ecoregions. In addition, the River Plate basin creates a biological corridor that helps spreading this subtropical influence even further south, down to the city of Buenos Aires, in the (not subtropical) Pampas.
The main subtropical ecoregions found in northern Argentina are the Atlantic forest (shared with Brazil and Paraguay), the Southern Yungas or "Tucumano-Boliviano forest" (shared with Bolivia), and the Great Chaco (shared with Paraguay and Bolivia), showing different types of forests, savannas and grasslands within them. Another subtropical ecoregion is the Ibera Marshes, not shared with any other country. Jabirus, hawk-eagles, forest-falcons, macaws, puffbirds, motmots, trogons, toucans, antshrikes, antpittas, manakins and tanagers are just some of the iconic Neotropical birds found in the north of Argentina, along with other fauna such as monkeys, anteaters, tapirs, jaguars, caimans, anacondas, piranhas and stunning butterflies, which complete the traditional tropical repertoir.