THE STRUCTURE AND NUMBERS DYNAMICS OF THE URBAN GOLDENEY (BUCEPHALA CLANGULA, ANSERIFORMES, ANATIDAE) POPULATION IN MOSCOW

From 1985-1998 to 2017, the numbers and structure of the urban population of the Goldeney (Bucephala clangula) were studied in Moscow City. Wintering birds and females with ducklings were counted on 150 ponds and 23 rivers of Moscow. Based on the age of ducklings, the date of the onset of egg-laying by females was calculated. The size of the wintering group has grown significantly since 1993 (r(s) = 0.92, p < 0.05, n = 25) and it reached 2400 birds by 2014. Since 2010, there has been a gradual shift of wintering goldeneys from outside the city to its borders. The numbers increase, like that of the Mallard, correlates with local climatic indices: the length of the frosty period (r(s) = 0.73, p < 0.05, n = 25) and the mean daily air temperature (r(s) = 0.42, p < 0.05, n = 25) and does not correlate with the global Index of the North Atlantic Oscillation. Goldeney and mallard breeding cycles are similar in the ordering of the egg-laying onset in relation to the transition of the average daily air temperature towards over 0 degrees C. The earlier the positive temperature established and the ice melted, the more time the females have to prepare for egg-laying both on goldeneys (r(s) = 0.80, p < 0.05, n = 18) and mallards (r(s) = 0.77, p < 0.01, n = 18). In the nesting goldeney group, in contrast to the mallard one, changes were observed neither in the timing of reproduction nor in the regulation of the negative effects of overstocking such as an extended egg-laying period and the reduction of brood size in response to the increased female numbers. The numbers of nesting goldeneys grew from 1998 to 2010 up to 57 broods, but then dropped to 4. The negative consequences for the local population are primarily associated with winter weather anomalies that lead to the death of hollow trees suitable for nesting. The goldeney population sizes in winter and summer vary in the opposite directions, this being caused by multidirectional trends in habitat transformation. The population dynamics of nesting goldeneys largely depend on the frequency of dangerous meteorological events, while wintering on the regional climate change.