Geographic variation of the storing behaviour in the Coal tit Parus ater: role of winter residency and environmental conditions

Foraging and hoarding behaviour of the Coal Tit Parus ater were studied in two widely separated populations, in the Pyrenees and in Norway. The two populations differed in their degree of winter residence and environmental pressures. Location of foraging and hoarding sites were described in the Pyrenees during winter, and during autumn in Norway where no hoarding takes place during winter. Significant differences in the hoarding behaviour of Coal Tits between these areas were observed. In the Pyrenees, birds hoarded on inner and lower parts of the trees, using trunks and thick branches as caching sites, which are the substrates most heavily used in conditions of winter environmental stress. In Norway, birds hoarded items on outer and higher parts of the trees, mainly among needled twigs, which were the substrates used in normal foraging. Animal food was hoarded more frequently by the Norwegian population. Our results show that hoarding behaviour varies among populations and suggest that the differences recorded may be related to differences in competitive pressures and the prevailing environmental conditions. Furthermore, the absence of a safe long‐term hoarding niche in the Norwegian population, due to interspecific competition, would make a strong sedentary habit difficult, offering a functional explanation for the differences observed in the degree of winter residence between Norwegian and Pyrenean Coal Tits.