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 food closer to the feeder and at a greater rate than did subordinates. When alone, the birds stored food closer to the feeder than when accompanied by conspecifics. Conifers were preferred over deciduous trees as cache trees. The subordinates cached more in the outer parts of branches than dominants. There were no significant differences in the relative or absolute heights of the caches, nor in the vertical or horizontal hoarding niche breadths between dominants and subordinates. We experimentally removed the dominants from the flock for 90 min and recorded the behavior of the remaining subordinates immediately after the removal. The removal resulted in a decrease in the hoarding distance of the remaining birds, indicating that the presence of dominants directly affected the behavior of subordinates and suggesting that klepeoparasitism by dominants may be prevented by caching farther away. With the dominants removed, the subordinates cached at a greater rate than before 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 subordinates do not benefit from changing their caching microhabitat. They might be excluded from those new possibly safer, microhabitats after the dominant bird rejoins the flock.