CONSERVATION OF HERONRY ARDEIDAE SITES IN NORTH ITALIAN AGRICULTURAL LANDSCAPES

Internationally important populations of night herons Nycticorax nycticorax and of little egrets Egretta garzetta are concentrated within a 5000 km2 region of NW Italy, where the landscape is intensively cultivated for rice, natural biotopes are reduced, and human impact is high. From 1976 to 1990 the heron populations increased, despite a decrease in the number of heronries mainly due to habitat destruction. The heronry sites differed from the unoccupied sites, in particular in their greater protection from terrestrial predators and from human disturbance. The heronries were evenly distributed, and there were indications that the location of a heronry is determined by food competition with neighbouring heronries. Our results suggest the following for conserving the heronries in NW Italy, and in other zones where natural wet biotopes are scarce: protection of the existing heronries, and the active management of their habitat in order to maintain suitable characteristics; creation of a network of new breeding sites, spaced at 4-10 km in relation to the available foraging habitats, in zones without suitable sites for breeding. The protection of unoccupied. suitable sites near the existing colonies has a lower priority, because these sites will not be colonized.