ОСОБЕННОСТИ ОРГАНИЗАЦИИ МНОГОЛЕТНИХ ИССЛЕДОВАНИЙ КАМЫШЕВОК РОДА ACROCEPHALUS В СЕВЕРНЫХ ШИРОТАХ НА ПЕРИФЕРИИ АРЕАЛОВ

Due to melioration at the lands adjacent to the Lake Ladoga and discharges of organic matter by various enterprises in the second half of the 20th century, a natural equilibrium in the coastal part of it was disturbed, which caused intensive overgrowth of the once large sandy beaches in the Svirskaya Guba of Lake Ladoga as a result of the removal of peat and other biomass. The formation of thickets of coastal vegetation significantly influenced the extension of the range of some species of Acrocephalus warblers in the northern and northeastern directions. Our studies actually coincided with their expansion in the South-Eastern Ladoga area.

The research was conducted in 1987–1995 at the Ladoga Ornithological Station of the Gumbaritsy full-time department (South-Eastern Ladoga area) on the territory of the Nizhne-Svirsky State Nature Reserve (Leningrad Region of the Russian Federation). Constant investigations were carried out on two controlled sites (CS), established in 1987. CS №1 is located on 400 m from Lake Ladoga in the area of overgrown haylands with ribbon curtains of willow stands, alder and birch forests and bounded on three sides by large massif of taiga forests. CS №2 borders directly with Lake Ladoga and is occupied with psammophytic, forest and marsh vegetation.

The studies included regular visual observations of marked individuals, registration of local breeding populations, search for nests and catching adult birds, and ringing of chicks and their subsequent control after departure from the nests. Annually, the completeness of control of nesting reed warblers on CS №1 was 96–98%, in CS №2 it was 92–95%. To assess the number of nesting birds and the density of their settlements on the CS, the method of mapping the territories was chosen as the main one.

So, in South-Eastern Ladoga area, most Acrocephalus species breed near the northern limits of their ranges. The conducted studies allowed to collect a unique material on the biology of local and transboundary reed warblers and to identify features of their behavior on the periphery areas, which were not typical for populations living southward.