Neotropical austral migrant landbirds: population trends and habitat use in the central Monte desert, Argentina.

CUETO, V.R., J. LOPEZ DE CASENAVE & L. MARONE

THE CONDOR

Año: 2008 vol. 110 p. 70 - 79

0010-5422

Abstract. We studied density variations of two groups of Neotropical austral migrant landbirds in the main habitat types of the central Monte desert of Argentina (Prosopis open woodland and Larrea shrubland) along 10 years: the temperate-tropical (SATT) and the cold-temperate (SACT) migratory systems. SATT was made up of five species, all of the Tyrannidae family, whereas only two of the seven species of SACT were from that family. Total abundance of both SATT and SACT was higher in open woodland than in shrubland. SACT abundance differed among years, reaching lower density in 1994 in both habitats. In subsequent years SACT species density increased, although did not reach values similar to those previous to 1994. The decline in 1994 coincided with a two-year drought period that began in 1993, but lower density in the following years was not related to climatic conditions in the study area, suggesting a low capacity of SACT species to recuperate population abundance after stress periods owed in part to limitations during the reproduction phase. In contrast, SATT density was not associated with local climatic conditions plausibly because SATT species were vagrant or used the study area as a stopover site. Birds of both migratory systems use disproportionately the open woodland during the breeding season. Structural complexity of the vegetation in that habitat offer more sites to nest and feed than the shrubland. Human activities in the central Monte desert promote “shrubbing” or the structural simplification of the habitat, therefore Neotropical austral migrant landbirds could be facing a critical scene for its conservation in this ecosystem.