Sexing of the little auk ( Alle alle L.: Alcidae) by the beak outlines

Our method of the distant field sexing of the monomorphic birds by the photographs turned out to be effective for the monomorphic little auks ( Alle alle ). Males statistically significant differ from females by the heights of maxilla and mandible at the border of feathers and in the middle of the beak. The diagnostic criteria in sexing the little auks are the ratios (indexes) of the upper and lower bill heights to each other as well as the values of the discriminant functions of the selected ratios. Checking the method on the photographs of the sexed little auks showed 100% of success.