SCIENCE
Although widely thought of as being an avian feature, the crop is a structure that is also found in a wide variety of animals, including insects, slugs, snails, leeches and earthworms. Obviously, it differs in structure depending on the animal.
The crop is one of the most interesting evolutionary developments in the digestive system of birds. That said, it is not present in all bird species. It is absent in pigeons and doves, owls and buttonquail (Turnicidae). In pigeons and doves, the crop produces a secretion called crop milk to feed the
