The eggs of the birds constitute a regular food in the feeding of the humans. They are protected by a shell and are rich in proteins (mainly albumin, which is the clear or white part of the egg) and lipids. They are a food of easy digestion, the main component of multiple sweet and salty dishes, and an essential part in many others due to its binder properties. The most consumed, with a great difference, are those of hen, followed by those of duck and goose. Also the quail eggs that are very small are consumed, as well as gastronomic delicacies or for small children. Ostrich and rhea eggs are also edible and can weigh up to 1.3 kg. Almost all of them come from industrial exploitation: poultry farming. Eggs used for human consumption are generally and largely unfertilized. Roe (such as caviar) are fish eggs and are also edible in many cases by various cultures.