Interactions of the influences of habitat protection, habitat heterogeneity, and periodic flooding on waterbirds of the lower Parana River, Argentina

摘要

How waterbirds respond to environmental characteristics of river systems is of interest because of the high biodiversity of waterbirds in these systems, their ecological roles, and the importance of waterbirds in hunting for sport or sustenance. We studied the influence of natural factors (water-level fluctuations and environmental heterogeneity) and human-related factors (habitat protection, which primarily excludes cattle grazing and hunting) on waterbirds in the Pre-Delta region of the Parana River system during three years. Our objectives were to evaluate the environmental factors that influence the assemblages of waterbirds and whether these variables explain differences in waterbird assemblages between protected and non-protected areas. Both species richness and abundance of waterbirds per point count increased with the diversity of land cover categories at count spots. Species richness also increased with the surface of open water. The larger surface of open water in the non-protected area contributed to explaining the higher species richness and abundance of waterbirds, including species with hunting pressure, in this area. During floods, the protected area maintained a high abundance of waterbirds, probably because the higher proportion of trees and aquatic vegetation in this area provided perches and foraging sites. We recommend enlarging protected areas in the Pre-Delta region because of their role of sheltering waterbirds during floods. Protected and non-protected areas serve complementary functions in providing habitat for waterbirds; therefore, it is important to maintain both of these management types in the landscape.