Waterfowls of Selenga river delta: selectivity nest habitats at various water levels

On the basis of long-term researches (1972-1982) one of little-known aspects on nest ecology of a waterfowl - selectivity nest habitats is considered. Work is executed in Selenga river delta throughout an 11-year-old climatic cycle including three different levels on supplying with water of territory - high, middle and low, with duration of each season 3-4 years. Inspection habitats were made proportionally to their interrelation in delta. The basic works are executed on a key plot, the area about 150 km2, had in its central part (between the basic river-bed of Selenga River of and channel Kolpinnaya). The account of nests was made throughout a full breeding season on the control grounds with total an annual discount area ~ 5,0 km2. They strongly differed on the area and configurations, but the least dimension of the ground was not less than 1,0 hectares. In different years of observation the quantity of the grounds fluctuated from 18 (water high levels) to 45 (low levels of water) without colonies which were treated separately and also contained a some quantity of waterfowl nests. During a season they were treated three times that allowed to reveal all of duck nests, including and repetitive one, appeared after loss of the first nests. The found nests were described under the standard schema [Skryabin, 1975], allowing quite definitely to carry them to this or that type of habitats. Stuffs are received for an operating time on habitat distribution of 13 species of the most ordinary nesting species of a waterfowls of Selenga river delta. The special analysis has allowed to excrete of the bird bunches using only certain habitat types, apparently differing at warious water levels. The causes of the revealed selectivity habitats, especially accurately showing are considered at various levels supplying with water of Selenga delta. The total amount of the collected materials compounds about 2500 nests. All collected materials are treated by the standard methods parametrical and nonparametric statistics [Sachs, 1976; Pesenko, 1982; Runion, 1982].