Today “Tract Trekhozerki” is a state natural zoological reserve of regional importance. The tract is home to over 100 species of birds, including 12 species listed in the Red Book of the Russian Federation. For five bird species, breeding information was obtained over the period from 2013 to 2018. In two species of gulls (Larus argentatus mongolicus Suskin, 1925 and Larus ichthyaetus), the abundance changes were similar: the number of breeding pairs decreased (in the second species to 0) from 2013 to 2015, and then there was an increase in numbers. The population of Ardea cinerea has decreased. Recurvirostra avosetta breeds irregularly in the tract, with 73 pairs nesting in 2018. For all these species, a decrease in the average size of masonry in years with a low water level was noted. Phalacrocorax carbo at nesting were noted only in 2013 and 2014. The changes in abundance are associated with cyclical fluctuations in the water level in water bodies: a decrease from 2013 to 2015 and a subsequent increase until 2018. This affected the availability of nests, the area of habitats suitable for nesting, and species competition. For species of birds listed in the Red Book of the Russian Federation (L. ichthyaetus and R. avosetta), the high, but not the maximum degree of watering observed in 2013 and 2018 is most favorable.
This paper presents the results of observations on the state of two bird species populations listed in the Red Book of the Russian Federation Recurvirostra avosetta L., Larus ichthyaetus Pall. The populations of these species in the State Natural Reserve Tryochozyorki Tract have been studied by the authors for 8 years. The wetland is a key ornithological area of international importance. The paper presents information obtained in 2020, which has been compared with the information received in 20132018 which was published. For R. avosetta L. the maximum number of breeding pairs (127) and the maximum value of the average clutch size (3,6) were noted for the entire observation period. The reproduction of R. avosetta L. started earlier than in previous years. For L. ichthyaetus L. a relatively high number (no less than 280300 pairs) and also the maximum value of the clutch size (3,0) were noted, the breeding time of the species turned out to be typical for this territory. The analysis showed a favorable state of the populations of these species. The previously stated assumption about the relationship of the studied indicators of the nesting biology of these species with the level of water content of the territory was further confirmed.
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