Abstract
The article presents the results of a study on the nesting biology of the Black-headed Gull (Larus ridibundus) in the North Kazakhstan region. The research covers the spatial distribution of nests, their structural features and parameters, as well as the oomorphic characteristics of eggs. It was shown that the nesting density decreases from the center of the colony to the periphery, which is due to competition for space and the advantages of collective protection against predators. The average nest diameter, diameter, and depth of the nest cup demonstrated moderate to high variability, reflecting adaptation to the climatic conditions of the region. Comparison of construction parameters and materials used with other parts of the range revealed significant differences caused by the ecological characteristics of the habitat. The oomorphic analysis of eggs showed variability in the length, width, and volume of eggs, which also correlates with regional conditions. Egg coloration ranged from brownish to greenish hues, providing camouflage against predators. The obtained data underscore the significance of ecological factors in shaping the nesting and reproductive characteristics of the Black-headed Gull.