Ecological aspects of the nesting life of the black-necked grebe (Podiceps nigricollis C.L. Brehm) in the forest-steppe zone of the Trans-Urals

The black-necked grebe (Podiceps nigricollis C.L. Brehm) is a nesting, migratory bird species, the number of which in the Southern Urals reaches 12 thousand individuals. From an ecological point of view, the named bird species belongs to aquatic birds and prefers aquatic and semiaquatic habitats. Being a waterfowl, the black-necked grebe has a complex of diving adaptations and is characterized as a specialized waterfowl. The literature analysis has proved that the knowledge of the ecological aspects of the nesting life of the black-necked grebe is insufficient. The nesting period of the annual life cycle was studied on the Kurlady and Smolino lakes located in the forest-steppe zone of the Trans-Urals. The average date of birds arrival at the nesting area according to 1988–2013 data is 19 April. The choice of breeding site leads to the fact that black-necked grebes form colonies in stagnant water bodies or with a slow flow of water. The water is fresh or brackish, with a certain pattern of overgrowth of vegetation and depth in the area where the nests are located. The presence of nests of black-headed gulls (Larus ridibundus L.) plays a special role in choosing a place to build a nest. Black-necked grebes and black-headed gulls form polyspecific colonial settlements. The laying of the first egg is carried out by the black-necked grebe in an unfinished nest, floating on the water and having a flat shape. At the stage of the appearance of the first egg in the nest, the elimination of eggs occurs, which can reach 44,1% (the biological center of the colony, 1989). On the periphery of the colonial settlement, the percentage of dead clutches is significantly higher, which can be caused by unfavorable biotic and abiotic relationships. Nests of black-necked grebes are completed from the moment the first egg is laid until the laying is completed. At a statistically significant level, the diameter of the nest and tray, the height of the nest, and the depth of the tray increase. The nest with completed masonry has a truncated-conical shape with a cup-shaped tray. According to long-term observations, the average value of the completed clutch is 3,8 eggs per nest. The reproduction in the composition of a polyspecific colony is accompanied by the establishment of biocoenotic relationships. The manifestation of topical, phoric and factory relationships, which can lead to individual and group elimination, has been established.