Distribuição de aves limícolas migratórias (Charadriidae e Scolopacidae) em estuários: preferência de habitats e estrutura das assembléias.

Abstract

Several studies report the use of estuarine environments by migrant shorebirds in South America. However, distribution patterns of these species among estuarine habitats have been little studied. Our study aimed to investigate the distribution of migratory shorebirds (Charadriidae and Scolopacidae) and the composition and structure of assemblages of several habitats in the estuaries of rivers Mamanguape, Paraíba do Norte and Goiana in the coast of Paraíba, Brazil. Nine sites were selected for counting birds, four in open beach habitats (in ocean front) and five in inner estuarine habitats (tidal flats, a fluvial island and artificial ponds in a shrimp farm). Visual surveys were carried out at each site with the aid of binoculars and a spotting scope. Statistical analyses were applied to answer the following questions: (i) did occur differences in species densities among habitats? (ii) which factor had greatest influence on variations in densities? (iii) how counting sites can be grouped based on structure and species composition of their assemblages of birds? 72 counts were carried out from September 2010 through April 2011, during which 13 species of migratory shorebirds were recorded: Pluvialis squatarola, Charadrius semipalmatus, Limnodromus griseus, Numenius phaeopus, Actitis macularius, Tringa melanoleuca, Tringa semipalmata, Tringa flavipes, Arenaria interpres, Calidris alba, Calidris pusilla, Calidris minutilla and Calidris fuscicollis. Density of species varied significantly among estuaries and categories of habitats, but not among months. The category of habitat was the factor that had greatest influence upon variations of densities. The assemblages of birds in open beaches were clearly different from the assemblages of inner habitats, with regard to their species composition and dominance pattern. The species with greatest importance on differentiation between assemblages of beaches and inner habitats were C. alba, N. phaeopus, C. pusilla and C. semipalmatus. Although we suppose that some factors not measured in this study may have exerted influence upon pattern observed, our results suggest that preferences between open beaches and inner habitats may be influencing distribution of species in estuarine landscape.