Baby doves are fed crop milk, which is produced in both parent birds' crop glands. The feed is created during the cycle of incubation. However, not all birds are able to produce the grayish milk. To compensate, parents consume large amounts of seeds and water when they are off the nest and allow the mixture to soak in their crop for feeding purposes.
The most critical period of a dove's life is when it is just born, as survival can be difficult the first few days. To keep the new dove warm, a parent must fluff the feathers on its abdomen. Feathers that are flat keep any warmth away from a baby dove. Therefore, parents must fluff out and preen the feathers to maintain the baby bird's health.
10,000 Birds defines the crop of a bird as a muscular pouch that is situated near the throat or gullet. Expandable in nature, the pouch is used to store additional food for later digestion and is an extension of the bird's esophagus. The crop can extend to the point that it can make a long-necked bird look like it has a short neck. Crops are not exclusive to birds. They are also found on leeches and in some earthworms.