Seed supply as a limiting factor for granivorous bird assemblages in the Monte Desert, Argentina

Seed availability may limit the size of granivorous bird populations, parti cularly in desert environments. Seasonal and annual fluctuations in the abu ndance of granivorous birds were studied at three sites in the Northern Mon te Desert, Argentina. The way in which these changes were related to seed s upply was also studied. Granivore abundance and biomass, as well as seed ab undance, were greater in winter. Changes in total granivore abundance were mostly because of variations in numbers of the most mobile bird species, al l of which were found to have similar patterns of variation in their abunda nce. Evidence suggests that during the non-breeding season, the most mobile species are able to track patches of high seed availability over long dist ances, whereas the abundance of less vagile species largely depends on the local ecological conditions. Seed supply is a proximate factor that limits the abundance of granivorous birds in the Monte Desert during the winter, b ut does not limit species richness. Granivore abundance was not correlated with seed supply in spring.