Population abundance and biomass of large-bodied birds in Amazonian flooded and unflooded forests

Little is known about the contribution of different forest types to the beta-diversity, abundance and biomass of the avifauna in lowland Amazonia. This paper presents data on the large-bodied bird assemblages of adjacent upland (terra firme) and seasonally flooded (varzea and igapo) forests in the lower Rio Purus region of central-western Brazilian Amazonia. We focus our analysis on 23 large-bodied canopy and terrestrial bird species from 10 families, on the basis of 2,044 bird sightings obtained during line-transect censuses conducted over a two-year period. Large toucans comprised the most numerically abundant large birds in terra firme and igapo forests, whereas macaws were the most abundant in nutrient-rich varzea forests that were seasonally inundated by white-water. The aggregate population density of all bird species in terra firme forest was slightly higher than that in varzea forest. Igapo forest, which was seasonally inundated by black-water, sustained the lowest population densities. Terra firme and varzea forests differed considerably in species composition and abundance whereas igapo forest shared many species with both terra firme and varzea. Our results suggest that Amazonian floodplain forests play a major role in the persistence and community dynamics of the large-bodied forest birds.