What is a Crop?
A crop is part of the digestive tract in many birds and some other creatures as well, such as insects and earthworms. Essentially, the crop acts as a storage container to hold food until it can be processed by the body. In some cases, you can even see the crop of a bird; baby birds especially tend to have full, bulging crops which can look like strange cancerous growths in the bird's neck to the uninitiated.
Birds are probably the most famous for having crops, although the crop works in much the same way in other animals. Essentially, since birds lack teeth, they rely on a pre-digestive system to process the foods they eat so that they can be broken down in the stomach. When a bird with a crop swallows food, it makes a stop in the crop, which softens the food before passing it to the gizzard, a muscular organ which mashes the food up, often with the assistance of small stones. Then, the food can be digested.
In addition to being used to prepare food for digesting, the crop also serves as a storage compartment, allowing birds to gorge. In scavengers, this can be extremely useful, as it allows the bird to glut on a good meal and process the food slowly. Other birds take advantage of the crop to eat a large amount of food and then dart to safety to digest it in peace, away from predators. The crop is also used to store food for young birds, with the parents regurgitating the contents of their crops on demand.
As you might imagine, the crop is quite muscular, and it is designed to expand, sometimes to many times its size. When not in use, the crop can often look like a normal part of the esophagus, until it starts filling up with food, in which case it swells out like a little balloon. As food is pushed into the gizzard, the crop shrinks again.
When the crop is full, it can often be felt. To feel the crop of a bird, you can gently place a finger on the bird's upper chest, right around the area where the neck meets the chest. If you rub the area, you will feel something which feels kind of like a sandbag, being very hard and obviously gritty. This is the crop, and if you check back in a few hours, it will probably have shrunk, unless the bird eats again.
Written by S.E. Smith
