Oological material from two Kharkov Region colonies, Zmiyov and Chuguyev, of the black-headed gull Larus ridibundus were studied with the purpose to estimate population variability for the following traits: egg length (EL), egg width (EW), egg shape index (ESI), asymmetry value (AV), egg mass (EM) and egg shell background optical density (ESBOD). There were no significant differences between the two colonies for the characters studied, average character values in Kharkov population were respectively 52.4 mm, 37.0 mm, 0.707, 22.1 mm, 37.3 g, 84.1 cB, the corresponding coefficients of character variation being 3.82, 2.76, 3.90, 3.71, 7.24 and 15.70%. By using starch gel electrophoresis of egg whites, the polymorphism of an autosomal ovoglobulin locus G3 was revealed both in the Zmiyov and Chuguyev subpopulations with the frequencies of allele G3A 0.567 and 0.543, and of allele G3B 0.433 and 0.457, respectively. In the Zmiyov subpopulation, the polymorphism of an autosomal ovalbumin locus Ov was observed with the frequencies of allele OvA 0.896 and of allele OvB 0.104. Polymorphic types of egg white transferrin (locus Tf) were not found in the both subpopulations. With regard to values of population similarity and diversity (1), genetic similarity measure, r, was found to be 0.973 with identity criterion, I, 4.7 (P > .05) that testified to the insignificant differences between two subpopulations studied. Significant differences (P < .001) between the Zmiyov and Chuguyev subpopulations were observed by using values of population diversity, mean allele number, h (1.80 vs 1.50), and rare allele share (0.100 vs 0.012).