Composition and Seasonal Variation of Bird Life in an Anthropogenic Environment (San Pablo, Tucumán, Argentina)

Abstract

Urban development promotes changes in the natural environment. The Transition Forest of Tucumán is one of the natural environments that has suffered a great number of modifications. The objective of our work was to increase the knowledge of the bird communities that make use of urban centers within that forest. At the study site, native vegetation, such as cebil, tipa, horco molle and sallow, coexist with exotic species, such as paltos, pines, palms and medlars. We carried out 112 censuses of fixed radio points of 30 m diameter, in urban parks and other public areas. Based on the literature, species were classified according to their residence status and to food type consumed. The structure of the community was estimated taking into account frequency, abundance, species richness and relative impor tance. We counted 2512 individuals, belonging to 78 species of 29 families. Of these, 17 species (21.79 %) were considered residents and 36 (46.15 %) migrants. The insectivorous guild was the most abundant (31 species), whereas the least represented was the nectarívorous guild with five species. Pitangus sulphuratus showed the highest values of occurrence during the whole period of sampling. During the summer, the most abundant species was Notiochelidon cyanoleuca (29.23 %), whereas Thraupis sayaca was the most abundant species in winter, autumn and spring (27,55 %). Species richness (50) was highest in the spring. These differences might be attributed to the fact that sampling occurred in an area where exchange of species takes place between the dry Chaco and the Yungas of Tucumán. This, added to the fact that the most visible species are well adapted to human presence, may explain the observed community composition.