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 po pulations differed in their degree of winter residence and environmental pr essures. Location of foraging and hoarding sites were described in the Pyre nees during winter, and during autumn in Norway where no hoarding takes pla ce 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 cach ing sites, which are the substrates most heavily used in conditions of wint er 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 Nor wegian population. Our results show that hoarding behaviour varies among po pulations and suggest that the differences recorded may be related to diffe rences in competitive pressures and the prevailing environmental conditions . Furthermore, the absence of a safe long-term hoarding niche in the Norweg ian population, due to interspecific competition, would make a strong seden tary habit difficult, offering a functional explanation for the differences observed in the degree of winter residence between Norwegian and Pyrenean Coal Tits.