The crop is a sac-like organ located just below the throat. It is highly muscular, and is used for storing food that the bird has eaten. When the bird eats, the food first goes into the crop, where it is softened and mixed with digestive enzymes. The food then passes into the stomach for further digestion.
Other functions of the crop include:
Producing Milk
In some birds, the crop is also used to produce milk for feeding their young. The milk is produced by a special tissue in the crop, and is high in protein and fat.
Protecting the Bird from Swallowing Objects
The crop also helps to protect the bird from swallowing objects that could be harmful. If a bird swallows something that is too large or too sharp, it will usually be stored in the crop and eventually regurgitated.
Regurgitation
Some birds, such as owls and hawks, will regurgitate the indigestible parts of their food, such as bones and fur. This process is called "pelleting" and helps the birds to keep their digestive systems clear.