The life cycle and number dynamics of the urban mallard population (Anas platyrhynchos, Anseriformes, Aves) in Moscow

Аннотация

The life cycle of the urban mallard (Anas platyrhynchos L.) population of Moscow was monitored from 1998 to 2015. The numbers of the wintering mallards and females with broods, as well as the number of ducklings in each brood, were counted in 150 ponds and 23 rivers of Moscow. The countdown method based on the age of the chicks was used to determine the date of the first laid eggs. During the study period, the crossing of the average daily air temperature of the 0°C threshold moved from the end of March or beginning of April to the end of February, and in recent years, to mid-February (r =–0.44, p = 0.06, n = 18). The number of breeding females over the same period rose from 250 to 900 individuals, whereas the number of mallards wintering in the Moscow inner water bodies increased from 3.8 to 21.5 thousand. The mallards started nesting significantly earlier (r =–0.60, r = 0.008, n = 18). In the years with an early onset of spring, the beginning of breeding in mallards coincided with that of the birds inhabiting the southern regions of Russia. The number of breeding females increased by almost 40% (Z = 2.22, р = 0.02) and the brood size, by 6% (Z = 2.04, р = 0.04). The early onset of spring accounted for 92.3% of the variance in the dates of the start of ovipositin (p < 0.01) and for 55.1% of the variance in the number of breeding females (p < 0.01). The relative number of May broods grew and that of July broods decreased. Over these 18 years, with the number of the nesting females increasing, the brood size decreased (r =–0.46, р = 0.05, n = 18) and the egg-laying period increased (r = 0.56, p < 0.05, n = 18). The total duration of the breeding season in the city exceeds that in different geographical points in nature.