SOCIAL INFLUENCES ON FOOD CACHING IN WILLOW TITS - A FIELD EXPERIMENT

We studied the food hoarding behavior of willow tits (Parus montanus), a scatter-hoarding passerine wintering in dominance-structured flocks , We examined social influences on microhabitat selection and spatial cache distribution at temporary feeders. Dominant adult males stored f ood closer to the feeder and at a greater rate than did subordinates. When alone, the birds stored food closer to the feeder than when accom panied by conspecifics. Conifers were preferred over deciduous trees a s cache trees. The subordinates cached more in the outer parts of bran ches than dominants. There were no significant differences in the rela tive or absolute heights of the caches, nor in the vertical or horizon tal hoarding niche breadths between dominants and subordinates. We exp erimentally removed the dominants from the flock for 90 min and record ed the behavior of the remaining subordinates immediately after the re moval. The removal resulted in a decrease in the hoarding distance of the remaining birds, indicating that the presence of dominants directl y affected the behavior of subordinates and suggesting that klepeopara sitism by dominants may be prevented by caching farther away. With the dominants removed, the subordinates cached at a greater rate than bef ore the removal. The decrease in the hoarding distance and increase in the hoarding rate were the only significant effects of the experiment , perhaps suggesting that, during a short absence of dominants, the su bordinates do not benefit from changing their caching microhabitat. Th ey might be excluded from those new possibly safer, microhabitats afte r the dominant bird rejoins the flock.