Social influences on food caching in willow tits: a field experiment

Abstract

We studied the food hoarding behavior of willow tits (Pcrrut montanus), a scatter-hoarding passerine wintering in dominancestructured flocks. We examined social influences on microhabitat selection and spatial cache distribution at temporary feeders. Dominant adult males stored food closer to die feeder and at a greater rate than did subordinate*. When alone, the birds stored food closer to the feeder than when accompanied by conspedfics. Conifers were preferred over deciduous trees as cache trees. The subordinate? cached more in die outer parts of branches than dominants. There were no significant differences in die relative or absolute heights of die caches, nor in the vertical or horizontal hoarding niche breadths between dominants and subordinates. We experimentally removed die dominants from die flock for 90 min and recorded the behavior of die remaining subordinates immediately after die removal. The removal resulted in a decrease in die hoarding distance of die remaining birds, indicating that die presence of dominants directly affected die behavior of subordinates and suggesting that kleptoparasitism by dominants may be prevented by rarhing farther away. With die dominants removed, die subordinates cached at a greater rate than before die removal. The decrease in die hoarding distance and increase in die hoarding rate were die only significant effects of die experiment, perhaps suggesting that, during a short absence of dominants, die subordinates do not benefit from changing dieir caching microhabitat They might be excluded from those new, possibly safer, microhabitats after die dominant bird rejoins die flock.