Dynamics of population and new nest adaptations of Eurasian Oystercatcher Haematopus ostralegus in the middle flow of Moksha river (Central Russia)
This article presents the results of a comparison of the abundance and distribution of oystercatchers of the continental subspecies of Oystercatcher (Haematopus ostralegus longipes) in the middle reaches of the Moksha River (central Russia Temnikovsky district, Republic of Mordovia). Bird censuses were conducted during breeding season in late XX and early XXI centuries with a gap period of almost 25 years. It is highlighted that the placement of oystercatchers and their number practically have not changed. The main factor limiting the number of oystercatchers, and especially their nesting, is the limited number of typical nesting sites (not overgrown beaches and islands) on the rivers. The nesting conservatism of oystercatchers, as well as uncontrolled human use of beaches for housekeeping (watering and resting places for livestock), especially noticeable until the end of the XX century, limited the growth of population. In recent years, this factor has decreased significantly, the number of cattle and, consequently, the load on the coastal areas have reduced. In addition, oystercatchers began to acquire adaptive mechanisms, in particular, they started to use uncharacteristic nesting locations, which allowed them not to depend on many negative factors that previously had an impact on nesting success. In XXI century, the nests of the oystercatchers were first found in places that are not typical for this species (on coastal cliffs, opencast mines, broken trees). Such breeding adaptations of the species can result in an increase of the population of oystercatchers and their settlement in the Republic of Mordovia.