Bird Conservation International

Research Article

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

Torbjørn Haugaasena1 c1 and Carlos A. Peresa1

a1 Centre for Ecology, Evolution and Conservation, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, U.K

Abstract

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 (várzea and igapó) forests in the lower Rio Purús 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 igapó forests, whereas macaws were the most abundant in nutrient-rich várzea 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 várzea forest. Igapó forest, which was seasonally inundated by black-water, sustained the lowest population densities. Terra firme and várzea forests differed considerably in species composition and abundance whereas igapó forest shared many species with both terra firme and várzea. Our results suggest that Amazonian floodplain forests play a major role in the persistence and community dynamics of the large-bodied forest birds.

Pouco se sabe sobre a contribuição de diferentes tipos de florestas aos padrões de beta-diversidade, abundância e biomassa da avifauna na região amazônica. Este artigo apresenta dados à respeito das aves de médio a grande porte em florestas de terra firme e florestas adjacentes sujeitas a inundação sazonal (várzea e igapó) na região do baixo Rio Purús da Amazonia centro-ocidental. Nossa análise, baseada num total de 2,044 observações obtidas durante censos ao longo de transectos, foi direcionada a 23 espécies de aves de médio a grande porte pertencentes a 10 famílias. As aves mais abundantes em florestas de terra firme e igapó foram os tucanos, e as araras as mais abundantes em florestas de várzea. A densidade de população agregada de todas as espécies na terra firme foi ligeiramente mais elevada do que na várzea. A floresta de igapó sustentaram as mais baixas densidades populacionais. Terra firme e várzea diferem consideravelmente na composição e abundância de espécies, visto que a avifauna do igapó é intermediária entre a da terra firme e a da várzea. Os resultados sugerem que as florestas inundáveis tem uma papel muito importante na manutenção das comunidades de aves de grande porte na Amazônia, e pricipalmente aquelas espécies que usam grandes mosaicos de floresta.

(Received March 02 2007)

(Revised June 11 2007)

Correspondence:

c1 Author for correspondence. e-mail: T.Haugaasen@uea.ac.uk.