Revistes Catalanes amb Accés Obert (RACO)

The role of alien plants in the composition of fruit-eating bird assemblages in Brazilian urban ecosystems

Juan Carlos Guix

Resum


Between 1985 and 2004, 91 wild fruit-eating bird species were studied in 11 urban areas of Brazil: 78 of these species were seed dispersers and 13 were seed predators. The most representative families of fruit-eating birds in these areas were: Thraupidae with 46 species, Tyrannidae with 19 species, Psittacidae with 11 species and Turdidae with 6 species. Several of these avian species (or part of their populations) are vagrants or visitors (wanderers) and migrants. At least 19 fleshy-fruiting plant species usually dispersed by birds were found growing spontaneously in urban areas: at least 8 of these were indigenous (autochthonous) to the region in which they were found, and 11 were alien (allochthonous). A total of 383 fleshy-fruiting plants were found on 321 plots: 275 (71.8%) plants belonged to autochthonous taxa and 108 (28.2%) plants belonged to alien taxa. In these plots, the fleshyfruiting plants that most successfully colonized urban environments were those belonging to autochthonous taxa, all of them small-seeded: Ficus spp. (Moraceae), Rhipsalis spp. (Cactaceae), Struthanthus spp. (Loranthaceae) and Cereus spp. (Cactaceae). The alien fleshyfruiting plant species that most successfully colonized urban environments were: Ficus microcarpa, Morus nigra (Moraceae), Eriobotrya japonica (Rosaceae) and Pittosporum undulatum (Pittosporaceae). The present study indicates that many of the non-nesting birds that visit urban areas in Brazil are frugivores-insectivores. The results strongly suggest that such birds enter built-up areas to feed on fleshy fruits produced by allochthonous species of plants, especially during winter. The major ecological consequence of fruit-eating bird movements into urban areas is that most of these bird species can transport viable seeds of alien plants in the gut and disperse them in natural and semi-natural areas.

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