Migratory Pattern in European Mallards (Anas platyrhynchos) Changes through Decades: Probable Causes and Number Growth of Wintering Ducks in European Russia Cities

Data on 3874 ring recoveries of European mallards together with the information on winter temperatures in southern Europe during 1958–2023 together with number dynamics of mallards wintering in Moscow City, Russia during 1985–2023 were analyzed in order to find the underlying factor (factors) that control the increasing concentration of mallards in big cities. A number of factors, related to the process of mallard migratory pattern change in 1958–2023, creates the complex picture with, sometimes, contradictory phenomena. Up to 1980s, i.e., approximately up to commencing of global warming, winter temperature at wintering grounds in southern Europe did not have essential impact on the mallard’s population distribution along wintering and breeding grounds. Approximately since the beginning of global warming the relation between winter temperature fluctuation in the southern Europe and locations of wintering and breeding places became clearer: increase of the temperature in the southern Europe caused the shift of wintering and breeding grounds eastwards and northwards. Mallard as a stenothermal species even prefers relatively cool areas for wintering. This shift, together with stenothermal mallard’s characteristic in conditions of not high temperatures creates increased numbers of mallards in winter within cities in the breeding range of European Russia.