A stable group of birds has been formed at water treatment facilities. Sewage treatment sites are a well-known nesting place for long-legged waders. Black-winged stilts are included in the Bonn (Appendix II) and Berne (Appendix II) conventions, the AEWA agreement. Listed in the Red Book of Ukraine (1994, 2009) (status – vulnerable). In Ukraine, it is under protection on the territory of the natural reserve fund. The arrival of black-winged stilts waders at the nesting sites was recorded in the second-third decade of April (April 23, 2020; April 17, 2021). Immediately after returning to the nesting areas, the birds begin to build nests and lay eggs. The first eggs in this population were seen on 01.05.2020, 07.05.2021. The process of laying eggs lasted until the end of the first decade of July (08.07.2020). The average clutch size in the nests of Himantopus himantopus decreased from 3.8 ± 0.1 (2020) to 3.5 ± 0.1 (2021). The average egg sizes and their limits have been determined for long-legged waders. The chicks hatched from late May (30.05.2020), throughout June to the first decade of July (02.07.2020). The chicks were able to fly in a month – 29.06.2020. The muddy site of the wastewater treatment ponds of Kharkiv supported Black-winged Stilts until early August. Later, the birds started post-breeding movements. The last adults with juvenile birds were observed on 13.08.2020. Stilts in some years may stay until early October. The reproductive success of the black-winged stilt increased from 35.6% (2020) to 38.8% (2021). On average, 1.3 ± 0.2 (2020) and 1.4 ± 0.3 (2021) chicks fledged from the nests. In 2021, the number of nesting stilts increased, which is apparently due to rainy weather at the beginning of the reproductive period. For the purpose of more effective protection, the nesting settlements of the stilt should be protected and the appearance of people in the nesting places should be prohibited.

Introduction.The anthropization of ecosystems is an important factor for the evolution of species and adaptation processes. Fulica atra L. is a fairly abundant species of wetlands in Ukraine. The adaptation of the coot to anthropogenic territories occurs during the winter period in cities, later birds remain in these areas for nesting.Purpose.To assess the current state of the coot population at water treatment facilities and Lake Novy Liman, which are the parts of the territory of the city of Kharkov. Studies of nesting biology of Fulica atra on Lake Novy Liman and silt sites of treatment facilities make it possible to assess the current state of the population of the species in the water bodies of Kharkov, as well as important for completeness assessments of the distribution of birds in wetlands.Methods. The studies were carried out in 2020-2021 during expedition trips to Lake Novy Liman and biological treatment facilities No 2 in Kharkov.Results.The nesting biology of the coot (Fulica atra L.) was investigated at the silt sites of water treatment facilities of the biological treatment complex No 2 in Kharkov and Lake Novy Liman in April-June 2020-2021. The reproduction biology of 73 pairs of coot was studied. To set the nesting density, a map with the coordinates of the nests has been created. The first eggs in clutches were found on average on April 16±1,4 at an average daily temperature of +5 ± 1,73 ̊Сat night and +20 ± 0,89 ̊Сduring the day in 2020 and on April 18±1,9 at +14,9 ± 3,08 ̊Сduring the day and +5 ± 2,76 ̊Сat night in 2021. Average clutch size 7,1 ± 1,13 eggs. First chicks: May 8-10. Average egg size (n = 223): 53,37 ± 2,56 x 37,05 ±1,45 mm. Vertebrates and birds of prey have been identified that can affect the breeding success of the coot.Originality.For the first time, a study of the breeding biology of the coot was carried out on the territory of treatment facilities and their surroundings.Conclusion.Wastewater treatment plants are an important place in the city of Kharkov, where birds undergo the process of adaptation to the anthropogenic landscape.Key words: coot, nestingbiology, egg laying, sewage treatment plants, Novy Lyman lake.