Ardea
Official journal of the Netherlands Ornithologists' Union

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Carrascal L.M. & Moreno E. (1993) Food caching versus immediate consumption in the Nuthatch: The effect of social context. ARDEA 81 (2): 135-141
We studied the hoarding behaviour of the Nuthatch Sitta europaea in wild during winter, and examined whether or not the trade-off between caching (external reserves) and consumption (internal reserves, fat deposit) in this species is a function of the social context in which the individual forages. We compared the caching behaviour of birds foraging 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 longer when in social than when solitary. The efficiency of caching (loss of the cache due to robbery or disturbance) also decreased when another individual was present. The results of this study undertaken in natural condition demonstrated that the presence of another individual was perceived by the Nuthatch as a source of potential cache loss. In a social context Nuthatches tended to increase internal reserves (fat deposits), also benefiting from the potential robber by sharing vigilance (conversion of scanning time into feeding time). If solitary, Nuthatches maximized external reserves (caches) for later consumption. We conclude 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.


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