The effect of food and shelter on habitat selection by granivorous birds over-wintering in shrub steppes of the northern Negev, Israel

Habitat structure and productivity are suggested as important determinants of community structure. We manipulated food abundance and shelter availability in an ephemeral community of wintering passerine birds by augmenting seeds and by adding a large bush to experimental plots in the northern Negev, Israel. In Experiment-1, we augmented seven 1-ha subplots with seeds for 5 weeks, keeping adjacent subplots as controls. We then switched treatments between the subplots for 4 additional weeks. In Experiment-2, we had five independent 4-ha plots, divided into four 1-ha subplots allocated to four treatments: Control, Seed Augmentation, Shelter Addition, and both Seed Augmentation and Shelter Addition. Species richness and bird abundance increased with food abundance, suggesting that birds either move into sites with more food, allocate more time to foraging in them, or both. Bird abundance and species richness were not affected by the shelter addition. Food abundance affected species diversity only during Experiment-2. These results indicate that seed abundance influences the habitat use and local abundance of granivorous passerines wintering in desert environments and suggest that wintering bird populations as well as bird movements may be affected by the distribution of food resources in our study area.