The shell colour of the eggs laid by pheasants is determined genetically and can vary from very light to dark brown. In general, four basic colours may be distinguished: dark brown, light brown, olive, and blue. A number of studies indicate that there is a relationship between the colour of pheasant eggshells and their quality. Pheasant eggs with different shell colours differ in terms of morphological (shape) and physical features (weight, egg specific gravity, yolk and albumen share and indices) as well as eggshell quality (thickness, strength, ultrastructure). Studies conducted by previous authors demonstrated a range of structural and physical properties of pheasant eggs. The microscopic structure of the blue-coloured shells demonstrates some abnormalities in the structure and thickness of the shell layers and the shells of these eggs are the thinnest. This may be the cause of poorer hatchability in blue-coloured shell eggs.
