BIRD ASSEMBLAGES IN TWO TYPES OF FORESTS IN THE FLOODPLAIN OF THE LOWER PARANA RIVER (ARGENTINA)

Heterogeneity in floodplains affects many aspects of biodiversity, including bird communities. In the Lower Parana River, the landscape is primarily made up of two types of forests: "Albardon" and "Barranca." The goal of the present study was to describe and compare the bird assemblages of both forest types in terms of species composition and structure, based on points counts conducted from March 2006 until March 2007. A total of 76 species was recorded across both habitats, including 68 in Albardon (2482 detections) and 59 in Barranca (2269 detections). Seasonal variation in species richness followed a similar pattern in both forests, highest in spring and lowest in winter, reflecting, at least in part, arrival And departure of migrant species. Family composition generally was similar in both forests. Differences were more evident at the species level as demonstrated by indicator-species analysis. Much of the difference in species composition between forest types was related to the presence or absence of species associated with aquatic habitats. Guild composition was very similar in both forests, differing primarily in the relative importance of species associated with aquatic habitats or more open areas, more than with respect to diet or substrate. Foliage-gleaning insectivores were represented by the most species in both forests, followed by arboreal frugivore-insectivores and terrestrial granivores. Most guilds appeared to show marked seasonal variation in abundance but patterns of variation generally differed between the two habitats. Accepted 26 July 2011.