The intensity of supplementary feeding in an urban environment impacts overwintering Mallards Anas platyrchynhos as wintering conditions get harsher

Abstract

Although urbanization poses various threats to avifauna, some bird species, including Mallards, are attracted to towns and cities as their winter habitats due to favourable temperatures and abundant anthropogenic food. In this study, we investigated how population dynamics changed in relation to winter harshness and intensity of supplementary feeding. The results indicated that the number of Mallards increased with the feeding intensity but the pattern differed in response to worsening of wintering conditions on water bodies with distinct supplementary feeding intensity. The ponds with low feeding intensity were occupied by fewer but more stable populations, suggesting the presence of natural food resources there, available for small number of individuals, regardless of winter conditions. On the ponds with medium feeding intensity, we observed a bell-shaped relationship between the number of ducks and ice cover. Unpredictable anthropogenic food on those ponds might not provide sufficient food resources, forcing birds to relocate when wintering conditions worsen. In such conditions, the ponds with a high feeding intensity attracted more ducks. We demonstrated that the wintering population of Mallards in urban areas is not solely influenced by ambient temperature but is also significantly affected by the intensity of supplementary feeding.