Territory Size and Population Density in Relation to Food Supply in the Nuthatch Sitta europaea (Aves)

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Abstract
Population densities of the nuthatch in autumn were positively correlated with the size of the beech mast crop. In an autumn with no beech mast, territories were about 3 times larger than in the previous autumn, when the mast crop was large. This difference could not be explained by the age structure of these populations. When sunflower seeds were provided (in an area with no beeches) territories decreased in size. Average winter survival of the population is not correlated with the beech mast supply in the preceding autumn. The birds in autumn assess the winter food situation and adjust the size of their territories accordingly. How the optimal territory size of individuals changes with the food density is suggested.