Acta Zoologica Cracoviensia, 24 (1979 - 1980)
The annual life cycle of Rooks Corvus frugileus Linnaeus, 1758 and Jackdaws Corvus monedula Linnaeus, 1758 in the town of Cracow
Abstract:
Rooks and Jackdaws form loose groups in the Cracow area all the year round except for the breeding season proper. They roost together and then fly in groups to their feeding grounds, proceeding by separate but constant routes. The breeding birds roost in the centre of the town, in the town gardens called “Planty”. An attempt was made to explain this choice of roosts by their favourable microclimate. The gradual foundation of pre-roosting places in the “Planty” is presented. The moment and manner of the abadonment of the roosts by the breeding birds on 12 October was observed. The reasons why Jackdaws build their nests much later than do the Rooks have been reduced to their method of providing themselves with building material. The setting-in of groundfrost brings about an invasion of Rooks and Jackdaws in the built-up areas to the town, in search of food. The birds clearly prefer places abounding in food and having convenient observation posts. The intensity of invasion increased each time with the increase in frost and in the thickness of snow layer.
