Ardea
Official journal of the Netherlands Ornithologists' Union

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Loman J. (1985) Social organization in a population of the Hooded Crow. ARDEA 73 (1): 61-75
A population of wing-tagged Hooded Crows Corvus cornix was studied in southern Sweden during the years 1974- 1979. Interest was focused on aspects of their social organization and behavioural ecology. Only part of the population studied were breeding birds. Breeding pairs were territorial during spring when non-breeding crows lived in flocks mainly in rather restricted areas. If a territorial crow died, its mate kept the territory and obtained a new partner, usually within a month. Pairs which had recently established a territory had usually spent the previous breeding season in the flock-area that was closest to their territory. It was also common for a pair to visit occasionally an area in the year before they established a territory there. Some crows became territorial at the age of two years but the majority had not acquired a territory at the age of three. Some pairs were usually found in their territories throughout winter whereas others were less restricted to it. This difference was probably related to differences between territories in possibilities to find food in winter. Most juveniles had ceased altogether to visit their natal territories by September in the year of hatching. I observed two juveniles which to some extent remained associated with their natal territories throughout their first winter. Juveniles fed in large flocks in places with concentrations of food during winter. Territorial crows were usually observed in smaller flocks and fed in areas without obvious concentrations of food. Older flock crows behaved intermediately in these respects. Most crows frequented large winter roosts situated up to several km from the crows' daytime feeding ranges. The crows assembled at gathering places before roosting. They left these more or less simultaneously for the roost. Smaller roosts, within two km from feeding places, were used in summer. Some flock crows but no territorials migrated during winter. Most migrants apparently wintered in Denmark. Annual survival was at least 92% for territorial crows and 73% for flock crows more than two years old.


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