Complementary use of a wetland and its surrounding landscape by waterbirds in south-central Chile

Abstract

Waterbirds are one of the most conspicuous components of wetlands, and are frequently proposed as bioindicators of the state of these ecosystems. However, the mobility of waterbirds allows them to make complementary use of resources found beyond the limits of permanent wetlands. Therefore, understanding the relationships between the conditions of waterbodies and waterbird populations, requires a landscape- level approach. The objective of this study was to assess the complementary use of a permanent wetland (estuary) and its surrounding landscape by a waterbird community in Central Chile. During three years, we seasonally censused the waterbird populations present at the estuary of the Carampangue river (128 ha) and, in addition, estimated the abundance of the same species in the surrounding landscape (3,952 ha) through 71 point-count stations. A total of 69 species of birds were recorded in the estuary, and 51 species in the surrounding landscape. The strong negative temporal correlations between the populations at the estuary and landscape are indirect evidence for a complementary use of the two systems, mostly driven by seasonal flooding in agricultural land. The seasonal use of landscape resources was more marked among Anseriformes and grebes. Using generalized additive models (GAM), we observed that the percentage of flooded area and non-flooded prairies were among the most important predictors of landscape use by most species. Our results reinforce the need to expand the assessment of waterbird populations beyond waterbodies, including neighboring habitats of potential usefulness for this group of birds.