Birds Project

Movement patterns of granivorous bird species in the central Monte desert, Argentina

The movement behavior of an organism determines the scale at which it perceives and responds to the spatial subdivision of its environment and is a fundamental element of population-level processes such as metapopulation or source-sink dynamics. Movement patterns in birds can range from random wandering to movements within a fixed home range. Random wandering is well suited for exploiting unpredictable, patchy resources, while maintaining a fixed home range is suited for exploiting relatively predictable resources. The former behavior is common among seed-eating birds inhabiting deserts, where precipitation is temporal and spatially variable and could be promoting a very patchy seed production. However, in southern Arizona there are grassland sparrows which tend to remain within a fixed home range, whereas others present a wandering behavior. At a regional scale, this combination of behaviors could be important for the coexistence of species using similar resources. In the central Monte desert we have suggested that seed availability is related to changes in the abundance of sparrows, and could be promoting migrant behaviors in some species (Marone 1992). For example, Poospiza ornata is a migrant that breeds in our study site (Ñacuñán) and spends the winter in the northeast of Argentina. Other species have the opposite pattern: they breed in Patagonia (southern Argentina), and spend the winter in Ñacuñán (e.g., Zonotrichia capensis australis). Finally, some species have seasonal changes in their abundance, which could implicate the migration of some portions of their populations (Saltatricula multicolor or Poospiza torquata). Thus, the study of movement behaviors of sparrow species inhabiting the central Monte desert is essential to the understanding of population and community responses to spatial and temporal variations in the abundance of the resource. Our research goals are evaluating if sparrow species in central Monte desert present a sedentary or a wandering behavior, and if these behaviors constrain habitat selection in this system.