| Popis: |
Between the extreme north of Chile and the island of Chiloe, there are approximately 300 coastal wetlands. Among them, there are estuaries where the largest waterfowl populations are concentrated, due to their high productivity and diversity of habitats. Around 125 species of birds, approximately 30% of the species that live regularly in Chile, use this type of environment, which makes them high-value sites for conservation of biodiversity. Because the Chilean coast is part of a major migratory route for birds in the Americas, the composition of the avifauna of these ecosystems is also highly dynamic. In addition, the uneven distribution of wetlands on the Chilean coast is reflected in the presence of a small number of sites with concentration of these birds, which are characterized by a good supply of food and the availability of safe resting places (e.g. sand bars). Population data of different bird species in four estuaries of the central zone (Itata, Reloca, Mataquito and Topocalma) indicate that, although the communities of aquatic birds (migratory and resident) are highly dynamic, they also have a very regular and predictable structure. The high degree of overlap in population trends of most species, even among non-migratory ones, suggests that these dynamics are largely due to regional trends rather than individual behavior of each estuary. Among the migratory species it is possible to detect some that settle throughout the summer in the estuaries of central Chile, while others use them only as a place of refueling during trips to and from more southern sites. Additionally, these estuaries have an important role as post-reproductive aggregation sites for many resident species, which apparently move from the country’s central valley wetlands. Information on the waterfowl use of estuaries of central Chile clearly indicates that the main role of these environments is to serve as a resting place for most birds. In addition, many marine species gather in these places for bathing, and that way clean the salt of their plumage. A large proportion of the birds that are concentrated in the estuaries, forages at sea, except for some freshwater birds (less abundant) that make it into these wetlands. Reproductive activity of water birds in these estuaries is marginal, due to unfavorable factors for nesting and the high degree of human intervention. |
