FOOD CACHING VERSUS IMMEDIATE CONSUMPTION IN THE NUTHATCH - THE EFFECT OF SOCIAL-CONTEXT

We studied the hoarding behaviour of the Nuthatch Sitta europaea in wi ld during winter, and examined whether or not the trade-off between ca ching (external reserves) and consumption (internal reserves, fat depo sit) in this species is a function of the social context in which the individual forages. We compared the caching behaviour of birds foragin g solitary or with another bird (conspecific or heterospecific). When solitary, the Nuthatch hoarded in a higher proportion than when in the presence of another individual. The time feeding was significantly lo nger when in social than when solitary. The efficiency of caching (los s of the cache due to robbery or disturbance) also decreased when anot her individual was present. The results of this study undertaken in na tural condition demonstrated that the presence of another individual w as perceived by the Nuthatch as a source of potential cache loss. In a social context Nuthatches tended to increase internal reserves (fat d eposits), also benefiting from the potential robber by sharing vigilan ce (conversion of scanning time into feeding time). If solitary, Nutha tches maximized external reserves (caches) for later consumption. We c onclude that the decision about the way energy reserves are generated by the species studied is dependent on the social context in which the individual is involved.