Fig. 1

Phenological events of the mallard and mute swan’s life cycle. Migratory mute swans start their winter migration between September and October, overwinter in Croatia between November and January, and begin their spring migration out of Croatia between February and March. Migratory mallards stop in Croatia from October to November during their fall migration through the Mediterranean-Black Sea flyway. The breeding period for the resident mallard population spans from May to August. The model considers migratory mallards as responsible for introducing Highly Pathogenic Avian Influenza (HPAI) into waterfowl communities in Croatia.