species richness, composition, abundance and diversity of birds were analyzed in different environmental units in the pre-delta national park (entre rios, argentina). three environmental units (non-flooded riverine forest, flooded riverine forest and wetlands) were sampled by point counts from march 2006 until march 2007. a total of 147 bird species and an average abundance of 1845 individuals were recorded. a significant difference among habitats was observed in species richness, average abundance and diversity. wetlands showed the highest richness and abundance values. both types of riverine forests exhibited a relatively low number or species, although the flooded riverine forest showed the highest average diversity values. both forests shared most species, and contributed with only 29 species (20%) which did not appear in wetlands, and with 22 indicator species. wetlands, with higher proportions of species number and abundance, constitute the most representative environmental unit. some forest indicator species were also recorded in wetlands because of the closeness between environmental units. the high number of additional species suggests a large amount of generalist species. an integral approach embracing all environmental units is needed in order to understand the dynamics of this avifauna.