The crop is a part of an animal's anatomy connected to the digestive system. It is used to store food before digestion. It is common in birds but also found in some species of snails and earthworms, and was present in some dinosaur species.
In birds, the crop is an expandable pouch found at the throat and often visible externally, especially when full of food. Not all species of bird have a crop. In pigeons and doves it is used to store food but also to produce a substance known as crop milk to feed their young.
Scavenging species like vultures and condors will often feed until they are completely full, and then fill their crop for later digestion. The crop gives the birds a chance to store food for later digestion which is advantageous when it is unknown when the bird will be able to feed again.
Other raptor species, like hawks, eagles, and ospreys, have a crop, but owls do not.
Birds that regurgitate food to their young use the crop to soften the food items before giving it to their chicks.