Eggs are laid by female animals of many different species, including birds, reptiles, amphibians, a few mammals, and fish, and many of these have been eaten by humans for thousands of years. Bird and reptile eggs consist of a protective eggshell, albumen, and vitellus, contained within various thin membranes. The most commonly consumed eggs are chicken eggs. Other poultry eggs including those of duck and quail also are eaten. Fish eggs are called roe and caviar.
