Ardea
Official journal of the Netherlands Ornithologists' Union

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Birkhead T.R., Eden S.F., Clarkson K., Goodburn S.F. & Pellat J. (1986) Social organisation of a population of Magpies Pica pica. ARDEA 74 (1): 59-68
A colour-marked Magpie population near Sheffield, England has been studied for eight years. The population comprised territorial breeding birds (19-26 pairs/km2) and 40% non-territorial non-breeders (floaters). Magpies were mainly monogamous: bigamy occurred twice. Territories were occupied throughout the year, but defence was most pronounced early in the breeding season. Adult Magpies were very sedentary: mean distances between breeding attempts in different years was 25-30 m for both sexes. Territories averaged 4.9 ha in extent and boundaries were contiguous. However, outside the main study area in a region with very few trees, adjacent territories were widely separated. Nest spacing tended to be regular. Natal dispersal was very low (< 500 m) with no difference between males and females. The home ranges of non-breeding Magpies often overlapped their parents' territory, and subsequently bred in an adjacent territory to their parents. Non-breeders lived in loose flocks and comprised mainly first and second year birds. Within flocks males were dominant to females. Dominant birds were more likely to subsequently obtain a territory and breed. Evidence indicates that the availability of two resources, food and nest-sites, playa large part in determining Magpie social organisation.


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