The effect of the temperature on local differences in the sex ratio of Mallards Anas platyrhynchos wintering in an urban habitat

The intensity of supplementary feeding in an urban environment impacts overwintering MallardsAnas platyrchynhosas wintering conditions get harsher

“…Mallards wintering in urban areas react to local temperature changes by altering their abundance (Meissner et al, 2015b) and sex ratio (Meissner and Witkowska, 2023). In this study, we also showed that ambient temperature and consequently ice cover had a significant influence on the number of Mallards wintering in the urban area.…”

“…The Mallard Anas platyrhynchos is a dabbling duck species, that has adapted to the urban environment, and extensively uses the waterbodies located there during different stages of its annual cycle (Jarman et al, 2020; Kopij, 2020; Meissner et al, 2015b). For overwintering individuals, cities provide higher ambient winter temperatures (Kalnay and Cai, 2003), keeping the surfaces of the waterbodies from freezing, and therefore allowing Mallards to obtain their natural food.…”

“…In urbanized areas, Mallards gather in large numbers in sites where people feed them (Avilova and Eremkin, 2001; Engler et al, 1988). Yet, the studies of urban overwintering waterbirds usually only speculate about the importance of supplementary feeding and its consequences for the population, without including it as a factor in the research design (Avilova and Eremkin, 2001; Meissner and Witkowska, 2023) but see: Polakowski et al, 2010). A number of conducted research support the existence of supplementary feeding consequences during winter, but mostly for land birds using garden feeders, particularly passerines, and the increase in population density is one of the effects reported in those studies (e.g., Fuller et al, 2008).…”

“…Moreover, supplementary feeding may contribute to species range expansion (Greig et al, 2017) and diversity of bird communities (Plummer et al, 2019). In case of Mallards wintering in urban area, supplementary feeding contributes to higher survival of females during the periods of low temperatures despite increased energy expenditure (Meissner and Witkowska, 2023). Thus, we suspect that the changes in the abundance of the Mallard populations wintering in urban areas might be a response to the worsening of wintering conditions, which may have a different outcome depending on the intensity of anthropogenic food provision, pronounced even at the local scale.…”

“…Additionally, higher ambient temperatures within cities may create fewer constraints on keeping the metabolic rate essential for maintaining the stable body temperature of endothermic birds, that finally lowers the costs of maintenance of individuals overwintering in the cities, compared to their conspecifics wintering in more natural habitats (Tryjanowski et al, 2015). The importance of ambient temperature changes and winter harshness were pointed out as main factors influencing the demographic parameters of the Mallard population either in the urban or rural environment, such as its size (Meissner et al, 2015b;Schummer et al, 2010), sex-ratio (Meissner and Witkowska, 2023;Pattenden andBoag, 1989) , andsurvival (Bergan andSmith, 1993;Manikowska-Ślepowrońska and Meissner, 2022).…”