Information concerning seasonal fluctuation in dietary habits and trophic resources of granivorous birds assemblages are scarce in the Chilean mediterranean zone. These data base are basic for understanding interactions betweens consumers and their resources, and potential competitors. Seasonal characterization in dietary habits of Zonotrichia capensis and Diuca diuca, the most conspicuous granivorous birds at the Chilean mediterranean scrubland, were conducted. Also, seasonal changes in their trophic resources (seeds and insects) and richness of winter granivorous visitors were studied. Zonotrichia capensis appears an opportunistic consumer of the most abundant seeds and insects. Diuca diuca appears as an specialist, consuming only seeds. The correlation between resources and richness of granivorous assemblage fluctuations reveals a dietary shift in Z. capensis according to resources fluctuations. Diuca diuca also modified its diet, but in according to an increase in granivorous richness in the area.